I did this boss model for Majestic some months ago, and now that it's published in exis magazine, here's his post . Too much work, but a total fun, i enjoyed a lot doing him.
To paint the texture i used the help of bakes from a model with details. The process was almost the same as with a normal map model. Here's the base subdiv model i builded + a fast sculpt, used for the bakes.
A variation color for the texture, changing only the color layers.
and some of the sketches y did in photohop with the wacom and with pencil+paper.