I stripped 20 used FAL magazines, and there is rust on several of the bodies.
What is the best way to get that off and refinish them?

Depends on if you want to refinish them yourself,or have a Shop do it..They would Bead blast the mags,then degrease,then (most likely/reblue),since that is how FAL mags are finished..You can use steel wool,w/a cleaner,then wash them using a detergent soap and brush,wash them off with clean water and dry..,heat them up,(DEGREASE THEM)ACETONE,TCE,or some strong degreaser should be used..Heat them up,and if you want to paint them,I suggest a Gun-Kote refinish sold by Brownells,then heat them to 300/325 for about an hour..That finish should hold up..I have about 35 mags with a bunch of NEW ones..Some are Parkerized,most are Blued,and others are Painted..With a FAL,you can refinish them however you want,as they will,if used, be scraped going in and out of the Steel Reciever of a FAL..Good Luck.. I don't suggest Perma Silk D with FAL mags,AR mags are made of Aluminum,mostly,and are refinished differantly..

Check falfiles.com  They have a search function and there are many threads about FAL mag refinishing. Yes, they accept AR owners there.