First try just pushing the pistons in and pumping them out repeatedly. This might cure it. You have to hold 3 of the pistons in while you pump each one out individually. While it's out, clean up the side surfaces of each piston.
Don't worry too much if a piston pops out completely - push it back & make sure you bleed the brakes afterwards.
If that doesn't work, you have to replace the seals (#60 for the Exup). Pop out all pistons. Make sure all are pumped out a bit before you pull any right out - once one's out you can't pump the rest.
Pull out rubber o-rings and clean groove they sit in. This will require a carefully bent small screwdriver [or a Dremel. Ed.]. Clean up pistons with Scotchbrite, plastic pan-scourer or VERY fine emery (careful). Clean piston housing with brake fluid or brake cleaner - if the latter, must remove caliper completely and blow dry with compressed air - don't want volatile solvents in the brake fluid!
If you can't get some of the pistons out after the first one, you'll have to do them one at a time. In this case, don't use solvent.
Replace all o-rings, pistons and seals. Filling piston housing with brake fluid BEFORE inserting pistons means less bleeding later. You need the fluid resevoir open, and will have to suck out excess fluid (use a Tampax?) as the level rises.
Reassemble. Bleed brakes. Ride. Bleed again.
For the pads - you should be able to see if they're glazed. Use a fine emery (say 200 or 400) to roughen up the surface.
NB. Brake fluid ruins paintwork & no doubt is horribly carcinogenic. It will get everywhere. Try to clean it off as soon as possible. Use a barrier cream if possible.
Roger FordWatch out you don't lose the o-ring which sits between the caliper halves or you'll wonder why your brakes are weeping fluid when you've put them together again.