I haven't printed minis myself on my fdm printer (successfully, at least -- I can't find a 0.1mm nozzle for my printer to really do it properly). But assuming you do get good prints, you'd probably want to eliminate layer lines first. There are a few ways to do this, but using an infill and then sanding is probably your best bet to preserve small details.
Otherwise, I'd suggest using a vapor chamber with acetone -- and this really isn't that bad to setup. You just take a plastic tub that won't melt in the presence of acetone, put some paper towels with acetone on them in there, and cover your models with the bucket. How long you leave them in there is gonna be a trick to figure out.
But that's kinda the fun part of 3d printing: endlessly tweaking processes till you find something that works. /s
Anyway, further than that I'd assume its just like regular injection molded mini painting.