If the toilet is old, stained and all beat-up, there's a cleanser called "ZUD" that you can get in the janitorial section at Home Depot and Lowe's (it can't be used with a Purasan). But if you have a holding tank, ZUD is the stuff to use for an old rust-stained ceramic bowl. One of my customers had gout, and the uric acid in his system had just about destroyed the inside of the toilet bowl. NOTHING would get the buildup off the inside of the ceramic bowl. His wife contaced me in desperation, and I suggested ZUD. She tried it, and marveled about how well it'd worked. Unlike many other cleansers that only contain fine pumice and/or chlorine bleach, ZUD contains oxalyic acid, and it really does a good job. Again, don't use it on a head that is connected to a Purasan, but for installations that are holding-tank only, it works like magic!
It's fairly cheap, too.