Do not wind the rear calipers back like your tightening a big nut it splits the mechanism inside for the handbrake adjustment and before you start make sure the boot has not got stuck on the piston and will rip and twist as you wind the piston back.
That's a great tip regarding the boot.. will make sure that isn't clinging on to the piston before I start, also hear a squirt of brake cleaner under the boot can help if its sticking.
I'm a bit confused about the first bit though mate, isn't the whole idea of the rewind tool to turn it (clockwise) whilst applying pressure, which in essence would be like tightening a big nut? Keen to hear more about that as the last thing I want to do is f**k my handbrake!
I bought one of these tools that a fair few others have apparently used with success.