I've been thinking of repainting some TF: Gum figures (half the stickers rubbed off on the first transformation) but the mold release is a problem.

How do I get rid of the mold release on plastic? Please don't suggest nail files, last time I used one I had to dispose of a fig because the file left deep scratch marks on the wings.

P.S. How do I get rid of plastic flash? They're on all of my larger projects and I don't know how to make them go away.
P.P.S. Which color of paint will be best to match the dark red plastic of Kabaya Rodimus? I'm not planning on painting parts that don't need to be painted, so the paint colors must be a very close match.

 

The same way as it's made with plastic scale models and tabletop miniatures. Disassemble your fig and leave it for a few hours in a warm water with detergent. Then wash it in a warm water.
Should remove the mold release and any traces of fat from fingers.

 

Which brands do you recommend?

 

Any dishwashing detergent, really. The stronger the better. They're made to not leave anything toxic on hands and dishes, so they leave paint and finish intact (well, not on some Chinese KOs, but these are losing paint even when you give them a funny look, so...).
Grey soap also works.

So far I was using it on everything from Games Workshop figures, through soft plastic Airfix soldiers to HasTak toys and there was never any problem with plastic not being properly cleaned.

If plastic is really sticky, you can leave the figure in for a night.