I'm slowly building up a CMG Ravager in between sculpting sessions (and disco ball installations).
Here's my usual basing technique. It's pretty simple. I usually use fender washers and Magic Sculpt, and then hand-texture the putty as it sets up.
So, I based a Critical Mass Arc Fleet Walker that I had put together previously.
Walker is set in the epoxy, I start up my tap-tap-tap routine with a rounded sculpting tool, and make several overlapping impressions into the epoxy. I try and avoid a uniform, "golfball"-like effect, by working the same area over in random patterns.
I'll primer and basecoat next.