So I take it you know how I did it?
Not 100% but rollling out the GreenStuff to one nice big flat panel would be a really good way to start. letting it air cure a while, then cutting and fitting out panels and placing them over the knob with the wax paper still attached would be a good second step. Letting it dry/cure a little (possibly 40W bulb and a tin can for 5-8 minutes) would be a good third step. Removing that Wax paper in preparation to gap fill etc and to hide the evidence would put you in prime location for the picture.
Anyway, I am sure that you did it in a slightly different fasion; but somewhere along those lines.
I wanna see the front next time, and he better have the big ass laples shaped out on the front of that trenchcoat, etc, etc. (JK)