I powder coat 357 mag and 44 mag cast boolits, it's a very cheap easy to do process once you get the hand of it... took me about 3 shake and bakes to get a good coating, and figure it out... just a learning curve like anything else.
Powder coating seems to hold up better than lube from the limited amount of lubed bullets I have shot, with powder coating I have never got any leading pushing 357 mag 125 gr cast boolits pretty hard. Sizing after powder coating has not been a hindrance for me, but I have just recently started casting, and didn't sink the money into a lube sizer... I purchased the lee sizing die, and opened it up to what gave me good results. It's hard to compare powder coating to lube... powder coating is similar to a jacket.. that's what it is is a polymer jacket, and using a hammer I have beat a boolit flat the powder coating stayed in place... the advantages of powder coating are cheap easy startup, high velocity if that's what your after, no leading, you don't have to worry about it coming off.
It's cheap enough to buy a bottle of red at harbor freight, and some airsoft bb's to give it a try. Edit to add I sent
Ret_Eng some 357 mag cast boolits powder coated to try, and he may have pushed them even harder than I did... regardless a cast boolit sized to .3595" powder coated has worked well in two different Marlin 1894c's
I have not had as good luck with my 1894s 44 mag, out of several cast boolits 215gr, 245gr, 310gr, 260gr only the 215gr will stabilize. That has nothing to do with the powder coating, and I have not gotten any lead from powder cast powder coated boolits in the 44 mag either.