I give any of you that paint a lot of credit. Sometimes it's black magic and even the smallest amount of oil or contamination on a stripped part will ruin your day. I stopped painting a few years ago and started powder coating my own parts and will never go back. As long as the metal is properly blasted and prepped, you can't go wrong and the finish is tough. Also, as someone mentioned earlier, use DOT5 fluid and you won't have to worry about the finish getting damaged if you get any drips on it. Whenever I rebuild brake systems, I thoroughly flush the lines and switch to DOT5.
Here's a CB450 caliper done in super mirror black:
and a GL1000 rear caliper done in sheen black:
No runs, no sags, no issues. Once they cool off after curing, they can go right back on the bike. Just bolt and go.
If you are planning to paint and have access to a media blaster, then by all means use it. Glass beading brake parts could be tough, however, since the paint is pretty durable. Stripping the paint and then blasting for profile might be the better way to go. Then wash the part thoroughly with a good metal wash and blow it dry. If you have an old oven that you can bake it in, do so for 30 minutes at 400 degrees and that will force any residual moisture out of the pores and also burn off any oils that might remain. Wear clean nitrile gloves while handling them prior to painting and that will keep the oil from your fingers off the clean metal.