S21, I have experience with CLR. I used to use it to do my laundry and clean when I rented a place with rusty well water. It did work on the tub/shower with out hurting it, now that I think about it. The valves aren't terrible but I think a metal brush will make the job a lot faster. Thanks
My skewer with sponge trick worked like a charm. I think I'll make a bunch up and sell them at one of those big marine stores for $50.00 each!!!