Thank you that’s very useful.I have the tool and it worked fine for me. I usually run the correct size drill into the peg holes first to clean out brake dust before using the tool. Usually you are supposed to open the bleed nipple and never re-use the fluid because as you wind the piston back, crud inside can get dislodged back into the brake line. The thread is very coarse and it's mean't to wind forwards easier than go back, but will with a little patience. If your pistons are that hard to turn I think I would have a good look at them because they can get seized up? Wind them back and forth a few times and see if it gets easier? If I do any work on brakes I'm always giving all parts a good inspection and looking for other issues like sticking pistons and pads seizing in the caliper.