Ive cleaned pistons with carb cleaner and a scotch brite. be sure to wear heavy rubber gloves, carb cleaner wil seriously screw up your hands. also taped them off and bead blasted. be sure to get the ring lands completely clean. you shouldnt HAVE to use file to fit rings but if youre planning on building more than one engine its worth it to get a ring filer. you will bet a much better seal if you fit the rings to each cylinder. also works well on budget builds to accomodate for just honing in decent cylinders. not recommended but Ive done it and had good results. Ive also just bored the needed cylinders and weight matched the pistons, just depends on how much it bothers you to blow up an engine. Powerhouse sells a ring filer that looks pretty good.
sweet - I ordered my rings and rods today - THANKS Motor Mikey! Now I just have to get the double key in the crank