It's been a while since the original Coloring Techniques tutorial, so I thought I would stick to similar subject matter and incorporate some new techniques and methods I've picked up since then.
I'm using SketchBook Pro 6 on a Wacom Cintiq 22HD.
Step 1: With the addition of Synthetic Brushes I've started building up quick backgrounds before I jump into the foreground subject. Something I rarely did in the past. For this image, I started with a black canvas and built up a hotspot for the ground plane, then worked in some greys. Not very detailed or time-consuming, but it's effective in that it determines light source right away, so I won't have to struggle with that later on.
Step 2: When the background is good enough, I merge the layers together and pull down the opacity so that I can see my pencil when I put down lines for the initial sketch on a New Layer.
Step 3: At this point, I create another sketch Layer to block in the absolute blacks, and another for Ellipses which will make up the rims. The Elipse tool is your best friend for wheels. Errors in ellipses very easily throw off the entire look of a sketch. That's why a lot of concept sketches have rims/ellipses that don't close. The sketch layers will be merged for easier layer navigation.
Step 4: Now more layers are added on either side of the sketch layer. Blocked in Grey is placed below the linework, and the white ellipses are dropped on top of the sketch, and will remain at the top of the layer stack.
Step 5: This exercise is more about coloring, so a basic sketch will do just fine. No need to go crazy over cleaning up loose ends. Now, I bring the background layer to full opacity so that I can see what's really going on with each addition of color. With a large standard Airbsuh (flow - 30%), I lay down a lot of paint in the mid range, or base coat color. On the same layer, I add a darker shade with the same tool to build initial form for the profile of the car. The Copic color editor is a nice tool for this type of work, as all the related tones are there at a single click.
Step 5: Adding yet another layer (I use a lot, probably 70+ for a drawing like this) I block in light grey for the dish of the rims. This layer also goes behind the sketch, so that I don't have to worry about erasing perfectly around the black areas.
Step 6: Lock Transparency of that layer (Found in the bottom right of the active layer in the Layer Editor.) This prevents paint from going anywhere except the existing paint/pixels on that layer. So with Transparency locked, I can go to town with my airbrush without worrying about making a mess. Dark tone to create shadow at the top of the rim, and bright white for a highlight at the bottom.
Step 7: *I realize that I put the red paint all over the background layer. So I deleted the background and re-imported the initial saved background as an image layer (Luckily.) I then reapplied the red value on a fresh layer. This will make things a lot easier down the line. On a new layer (on top of the red, still below the sketch, I throw down some light orange to hint at highlights from the top-down light source.
Step 8: Now I can take a Hard Eraser to create a sharp edge for the bottom of the highlight which makes a surface break/belt line pretty quickly. Again, being on a fresh layer, makes this very easy. Once the paint is cleaned up, I feather back the intensity of the highlight with a large Soft Eraser.
Step 9: Back to the base red layer, I cleaned up the bottom with the Hard Eraser and added some more grey to the roof panel to break things up a bit.
Step 10: Now, I go down in the layer stack and create a brighter highlight layer above the background. Drop down some darker greys for a hard shadow under the car. Experimenting with the Synthetic Brushes again, I drag some white down from the wheels. Not sure if this will last.
Step 11: Back to the Rims. Creating a new layer above both the sketch and the rim/dish gradient, I throw down some quick lines with a custom tapered Paintbrush. The focus here isn't to go super accurate or realistic. I just want to get the idea of a concave face to this wheel by pulling the lines from the center hub to the lip of the wheel. Perspective plays a big part here.
Step 12: Similar to the rim earlier, I lock the transparency of the spokes and hit the center with a black Airbrush. Then cleaned up the strokes that extended beyond the white ellipses (Still on their own layer.) On a Layer below the spokes and above the rim, I use a narrow Airbrush to block in some shadows for the spokes, which is a simple way to illustrate form. I used to struggle with wheels for hours, but now this is my go-to-method when I'm working with quick concepts.
Step 13:At this point, I lay down some heavy white above and below for significant highlights. New Layer, so as not to worry about botching anything beneath.
Step 14: I drop the opacity so that I can see what's happening and erase back using the initial belt line as a reference, and clean up the top edge of the car. Pretty repetetive workflows, but simple can be effective.
Step 15: Navigating down the layer stack, I find the grey layer from earlier, lock transparency and build form with a dark and light Airbrush. Back above the highlights, on a new layer, I use a solid black paint brush to describe a hard shadow created by the rear view mirror.
Step 16: A few steps combined here. First off, I wasn't happy with that wierd highlight thing happening at the wheels. I wanted to bring focus back to the car itself. So I got rid of the white smudge layers, and added a crisp black shadow. I sharpened up the edges of the mirror shadow and softened up the whole effect with a Soft Eraser. Added a new highlight layer for a little mirror reflection. This doesn't really make sense based on the lightsource, but I think it adds to the whole thing. Thirdly, I added some darker tones to the Red base layer, and pulled out some body/surface details with a combination of the trusty Paintbrush, Airbrush, Hard and Soft Erasers.
Step 17: At this point, I'm not really feeling the red overspray 100%, but I don't want to lose it entirely. So I make a duplicate of the layer, turn down the opacity of the duplicate and erase back all of the excess paint from the original.
Step 18: This step is something I've been playing around with recently. I created a new layer on top of the background and dropped some perspective grid lines to hint at a tile pattern for the ground plane. Made a duplicate of that layer, locked transparency, painted it all white and moved it below the original. Then I nudged the whole layer down a few pixels to suggest a partline/cutline feel for the tiles.
Step 18: I can now use the tiles/grid as a reference to step up the reflection/gloss of the car. Using the same workflow, I built up the reflected lines and a duplicate white layer. Underneath those 2 layers, I feathered in some white airbrush to pick up on the ground highlight. Again, using the same method, I solidified the door panel and trunk cut lines.
Step 19: I grabbed the 3 separate layers for the rims, duplicated and Flipped Veritcally. Used some Transform to position them properly, and did some work with the Soft Eraser and a bit of red Airbrush for further reflection.
Here's the final result. All in all, this image took about 2 hours. Click on this guy for the full-res version.
I hope this tutorial had some tips/tricks that you might find useful in your own work.
This one was done in SketchBook Pro 6, but the tools and techniques used can be found in most versions of SketchBook.
If you have any questions or suggestions for tutorials, feel free to drop them into the comment section. Thanks for looking.