Tips to reinstalling caliper piston?

Anything beyond using brake fluid to help lubricate it? I already tried once and failed. I took a brass wire wheel to the seal rim again and shot it with some more brake fluid but I really don't want to go through the process of removing the thing again if it gets stuck

 

You took a brass wire wheel to what? Not the best idea, but you probably didn't cause any harm.

Did you install new seals?
Did you lightly poilsh the piston with 2,000 grit finishing paper?

Take either the bleed nipple out, or remove the banjo bolt, or both (assuming that you haven't removed them already).
Lubricate the seals and the piston with brake fluid. Start the piston in (solid end goes into the bore, hollow end faces out)
As soon as you are sure that the piston is in straight, and you can't push it in by hand any more, put a large C-Clamp on it. The screw end goes into the hollow of the piston. and the cast end goes on the back of the caliper. Slowly turn the clamp to push the piston home, making sure that the piston continues to slide in straight. If it's cockeyed, stop, remove the clamp, pop th episton back out with air or grease, and try again.