Since my first 944 I have done something different...
I bought a black-oxide kit from Eastwood. First clean the rotors really, really good. Some come with a coating of cosmoline oil. If necessary, throw them in the media blast cabinet. BE CAREFUL on rotors that have built-in bearing surfaces, such as early brake rotors for some VWs and audis if you go the media-blast method.
After drying, soak the rotors in the black oxide fluid for a minute or two. Slosh it around a bit to make sure you get it in all the areas of the rotors.
Then rinse off with water. Not for too long. Air-dry the rotors.
Then soak in the sealant for a minute or two.
Rinse again, dry and install. The look is pretty cool. It's almost like bluing on a rifle, if you've ever done it. And it also stops the rest of the rotor from getting nasty surface rust.