I bought my car used and the housing of the calipers were all rusty in addition to the rotor hats. I tried MGP caliper covers first and it looked too ricey but they also did not fit with my VMRs. So, I reverted to Rust Oleum 248659 Rust Reformer which converts the rusty area (after sanding) into a flat paintable surface. I then bought high temp (1000F) oven paint at Ace Hardware (flat black). They (caliper housing and rotor hats) look good and no signs of peeling and if they do I have plenty of paint left over.
Sorry, bad iPhone pics, Winter setup, and they need a good cleaning. I'm considering StopTech or Forge next year. They are 1000x better than they were (all rusty):
