One of the most interesting, simple and effective product out there is a product called Shaw’s Pads® Toilet Ring Remover.
These pads use no chemicals, are safe for septic systems, and work on an old principle called “elbowsus lubricatus,” Latin for “Elbow Grease” (I know, not really). Anyway, these pads have a short handle and a special pad. You wet the pad, use short vigorous strokes and the scale and staining comes free from the porcelain. It’s then flushed away.
You can buy them direct from the manufacturer or use their Ebay store.
For under $10 bucks you’ll be on your way to a stain free porcelain existence.