You would need to make sure that you pull the calipers off, strip them down as though you were going to rebuild them, clean them really well and then make sure that when they powdercoat them they don't get any of the color material into the inside of the caliper, bleeder whole or anything else like that. Then you would need to order the rebuild kit and do the rebuild. Thats usually why people go with caliper paint since they can use a small enough natural hair brush that they don't paint parts that shouldn't be painted and it doesn't require you to rebuild the caliper or even take them off of the car.

 

Brake paint will come off just as easily as regular paint with some steel wool and machine oil, or sand(bead) blasting, which is the easiest way. Definitely take off the yellow B4 painting them black, you'll be glad you did a year down the road.

 

If you painted them with Foliatec then good luck cause that stuff is extremely durable. Spilled some on the garage floor when I did my brakes and ended up having to take the air sander to it.