Most paint in situ, myself included. If you use a brush you won’t gunk up anything that should be free to move. Use a tiny artists brush and a half inch brush and you’ll be away.
If you want to spray then you really should remove the caliper s and strip them down. May as well get new seals etc too if you do go down that route.
Tom, you rascal, it appears that you've added an accent color to the calipers. Stop raising the bar!! Do you recall the actual name of the paint from Foliatec? Thank you, sir!!