i have done loads of these calipers. and i haven't had any issues on bleeding. and i dont use a piston tool either. i use to remove the pads. and put a thin board in between where the disc runs. and then i push the brakeleaver and forces the pistons out so they push on the board, but not so much that they pos out. then i can wiggle them out with my fingers.
i use some special grease for the seals. loctite 8104.
if there are "light surface" corrosion i use some very very very light wet sandpaper. grid 4000 or like that. so im sure not to take anything else then the corrosion.
2004 ZX12R B3