My son did mine with a wire brush first, then give them a blast with brake cleaner and then use high temp paint.
One thing he always does is remove brake pads and clips ect, hate to see them painted only do caliper and carrier. paint is available in other colours, found the seller excellent
http://www.ebay.co.uk/itm/SILVER-HOOK-HEAVY-DUTY-BRAKE-AND-CLUTCH-CLEANER-500ml-SGBC1-/320892772737?pt=UK_Car_Accessories_Car_Care_Cleaning&hash=item4ab6b32181
http://www.ebay.co.uk/itm/FERRARI-RED-BRAKE-CALIPER-PAINT-METAL-STEEL-ENGINE-High-Temperature-125ml-Tin-/160958550737?pt=UK_Body_Shop_Supplies_Paint&hash=item2579e092d1