first thing I would do is wrap a rag around the brake reservoir and leave the cap open. Brake pads I would just stick with oem ones.
You can use a c-clamp with the old brake pads to press the cylinder back in.
The rear pistons are the screw type design you mentioned.
you can also use bendex ( or bendix ) brake pads. They are good to. I used to use those on my stock rotors.