When you say your doing a refurb do you mean you are replacing the pistons? If so they should come with a seal kit.
Get the calipers bead blasted and then powder coated, make sure the people doing the powder coating (who will also be able to do the bead blasting) pack the holes for the pistons and bolts.
I dont know which calipers you have nor the cost of the pistons (stainless steel?) or seal kits, but it might be worth checking out biggred first, before buying the kits and getting them powder coated.