I was getting some front brake fading and very long lever pull at a previous track day. Nothing like pulling the brake to you knuckles at the end of a straight.
So I decided to upgrade the from brakes. Purchased a new Brembo radial MC, EBR slotted rotor, EBR hardware, 2015 Compound pads, Motul 600 fluid and removed the caliper springs.
Wow, what a difference. The improvement in feel and the bite that the 2015 allow are so much more confidence inspiring. Kind of expensive but one of the best mods thus far.
I have always cleaned the pistons in a similar manner. Afterwards, I spray a small amount of silicone spry into the piston seal area and let dry. It pubs the rubber parts a bit and really smooths things out.
The real problem I had was the MC seal were going bad.
old school...like polishing spokes - use a shoelace soaked in brake cleaner...pull the pads and put a piece of plywood in there ( not too thin ...not too thick..."just right"(5/8"?))pump the caliper up...wrap the shoelace around the exposed piston(s)...buff 'em clean with the lace...also clean the back of the pads while they're out...best fix is to rebuild the caliper ..the kit (from EBR) isn't too costly.