cleaning a toilet help needed!
HOLY SMOKES!! How does a toilet get that dirty??
....don't answer that question
I'd attack that in a gross decon fashion first -- diluted muriatic acid and a stiff brush. Flush, repeat. Flush, repeat. Don't forget gloves, eye, and respiratory protection! Get it as clean as you can with that stuff, then finish it up with pumice. As stated, pumice stones are made for this, and blast through hard water stains like butter and leave the bowl looking like new. It's rather impressive.