Okay, but without pictures to show the various steps I'm not sure how well I can communicate the whole process. Please feel free to ask additional questions. I'll share whatever I can.
This unit was designed relatively late in the Shadow Revolution lineup, so we knew what the various materials, team colors, weapons, and wheels would look like. We reused wheels not only to keep the look consistent but to reuse textures so less had to be loaded into video memory.
1. I started with rough sketches for a heavy scout unit with anti air capability and two firing modes. The alternate firing mode was a 'level break' style super attack, so it was important to convey this visually. At the tiny size the unit was on screen, the best way to do it was have extra guns come out and radically change the silhouette.
2. I made a low poly proxy model to figure out the transformation of the turret. This would be difficult to do with just drawings, and foolproofs the process of handing off the design to be modeled by somebody I wasn't working closely with. It also let the designers have a proxy unit they could use in prototype builds in hours rather than days.
3. I rendered out the model in 3DS Max from a standard camera location with the same lighting as the rest of the units. This let me copy and paste elements that were to be reused from previous units such as the wheels with minimal need to redraw things. This is important in something like an RTS where you have to design a lot of units with not a lot of time and a need to be stingy with texture space.
4. The paintover part itself is pretty straightforward. Usually just a round brush and colors sampled from the pasted elements. I'll usually use another layer set to 'Screen' or 'Overlay' with a noise texture (usually metal scratches) to make it less flat. When it's done I'll add a 'Linear Dodge' layer on top and use a big, low opacity brush to make some elements come forward and mimic the lighting model of the engine.
Hopefully that's on some use. I'm happy to answer questions about any of it. Thanks for being interested.