What do you mean exactly? If I understand your question the way I think I do here it is….
I use a belt sander to rough the parts down (I'm lucky enough to have access to one)....I use a piece of sand paper to finish sand afterwards. You could also hold the part in a small vise (lightly) and use a Dremel tool to sand off the back...or just hand sand them which takes a while…
Paint....wash parts after sanding with dish soap and warm water....dry them (I air dry mine) and then paint as normal
Glue must be super glue...regular glue doesn't work on resin....
Hope this helps
Pray for Surf!
Proud sailor (USNR) of IBU 21...NCW Group2