If you want calipers that look awesome then remove them, wash them and dry them well, as noted by others, and then sand them lightly with 3000 grit, primer them and then paint them using paint designed for high temps.
Instead of using a paint brush or a can use an airbrush. An airbrush gives fantastic results. The cost is not all that expensive and because there is very low overspray you can spot repair without tons of masking.
Anthony