220 w/ any foam isn’t fine enough. You’ll definitely have to go down to 600 with the feather touch. Also depends on what foam, there are different density yella’s. Try to find a more dense one, it’ll be heavier than what you have now and will hold details better. I found one that’s about as porous and holds detail as much as blue REN but it’s easier to sand and isn’t as heavy. I wish I could give you a brand name, I borrowed scraps from a client, didn’t have the manufacturer info. Only use that overly porous stuff for general size/shape exploration studies. Once you have that figured out, go to ren. It’s harder to work (and more expensive) but the results will be better and you’ll spend less time w/ extra processes to paint it. Plus you’ll have a model that won’t crush when some idiot plays with it and doesn’t realize that it’s fake and that the battery cover won’t come off!