TAMS said:Good old fashioned elbow grease using a pumice stone with long rubber gloves worked for us

Luckily hubby volunteered
I second the pumice stone idea, someone recently told me this and it really works... also I've heard dropping alka seltzer plus tablets in the bowl and them for a bit then should scrub easier, though I haven't tried that one myself yet... Mike's toilettes get like this because of the well water
good luck hun!!