To make 100% hets, you breed a visual pied to a normal female.

To make pieds, you can do several things:
100% het to 100% het
Visual pied to 100% het
Visual pied to visual pied
or prove out possible het pieds by breeding a 100% het pied to a possible het pied, or a visual pied to a possible het pied - or if you're really wanting to play the odds, breed two possible hets together and HOPE they prove out.

This may help you:
http://www.ballpython.ca/genetics.html
Pieds are recessive