I use a slightly different technique to Jason...I put a layer of cloth behind the damaged area, chip away the resin from the cracks so you have no loose bits, apply thin zap to the exposed cloth area to make sure it's wicked in and firm, then fill over the top. I use either fine surface car body filler (yep, I know it's polyester based but it makes no difference at all...it will stay stuck on epoxy mouldings with this type of repair!) or Squadron Green (or white) putty (from the model shop...the plastic builders use it). Prime and paint and that's it.

Cheers,

Dick