Hi,
Where are you based? I refurbed my own R32 calipers they are pretty easy to do. Split them in half by removing the 4 bolts, you can clean the aluminium block and piston by hand and with mild cleaners.
I had a friend shot blast the blue section with fine blast, i then cleaned with alcohol based panel wipe and handed them over to the powder coaters, the colour looked almost day glow pink but once baked they turned out a lovely signal red. Most powder coaters will also shot blast and the total job wont cost the earth if you do the prep work i.e splitting them.
Rebuilding is slightly harder, you need a vice and something to prevent marking i.e softwood block, the trick is to secure the painted section and bolt the alu caliper back on, a good pinch with a breaker bar is enough torque to hold them together, you dont want to strip the threads.
dont forget new stretch bolts for mounting them to the car. simples
