how are the pads?if your down to the last bits there may be a buildup of gunge(old brake pad dust and road debris) on the pistons that make them stick a bit cause theres a lot of piston sticking out of the caliper.
new pads if needed and clean up the pistons will sort it.
I have used fine wet and dry before on some pretty old pistons just makes the baked on crud come off easier but if they have some yuppie coating on them i would be inclined to use something less abrasive and when there all clean looking lube them up with brake fluid and push them back into the calipers with your finger.
Probably will need to bleed the whole system after that one.
Also a good time to look at stainless brake lines while you are at it.