What's the best way to get all 4 pistons out?
Maybe splitting the caliper and doing it that way with compressed air?
Best way appears to be to push out the pistons on both sides before you disconnect the brake line leaving a gap between both sides. Then remove from the line and then take the caliper apart. Using a piece of bicycle tubing to protect the pistons, pull them out. I've inserted links for a 4 piston caliper rebuild for anyone interested.
http://youtu.be/EDfNb_9YkcIhttp://youtu.be/DC_Id6rgP3g