RE: Thinning epoxy with Acetone and adding filler?
I just buy extra strength ACE Hardware brand Acetone and it has always worked great for thinning epoxy and Z-poxy finishing resin for glassing. I have worked with fiberglass since I was 10 yrs. old and 47 years of it I have always thinned my West Systems resin and hardner with acetone. It helps to penetrate the balsa for wood models and it makes rough sanded fiberglass boat repairs much stronger. I rough up the boats surface after Ive gone through the gelcoat and then add new glass. I blend it in and then shoot it with matching gelcoat. Buff it to blend the surface color and shine and it's done.
Barry
I think I opened a can of worms with this thread because it seems everyone does it different!