What's the best way to remove stubborn stains from toilets? The first thing to do is to empty the bowl of most of its water using one of three methods:
Take a bucket of water and pour it rapidly into your bowl — this drives most of the water down by sort of a manual flush — enabling you to work directly on the stains.
Another method — the most convenient — is to take a bowl brush and ram the water in a controlled way down the toilet trap ten or fifteen times until all the water's out except a little pool at the bottom.
A third way you can do it is to take a plunger and plunge the water down the trap.
In each case, your objective is the same: emptying the bowl so you can work. Then sprinkle the inside of your bowl liberally with cleanser and give it first a general cleaning using a bowl brush. Rinse the bowl by taking water from that little pool at the bottom. Then take your pumice stick and work directly on the deposits. The pumice stone is a great tool because it is softer than the porcelain but harder than the deposits — it won't scratch the bowl; but wet it before using it to be safe and to make it easier to use. Work until all the rings and stains are gone.