I use a $50 lisle pad spreader from amazon. Works great but it pushes on the tabs of the pads and I was hoping I could insert it into the caliper and push on the pistons.
But, it works great. Only issue is that if you need to FULLY retract the pistons for brand new pads on brand new rotors, you may have to wait for a second because the spreader has barely enough range of motion to get the pistons pushed all the way in.
I'd link my thread but nature is calling really loudly...
2015 F34 328iX GT Glacier Silver
2011 E90 M3 Monte Carlo Blue
2004 E46 M3 Imola Red