I use Caylx manifold dressing. Its probably nothing more than what HRL's "stove polish" is made of.
I use The dark gray engine paint available from thefillingstation.com on the rest of the engine and the intake manifold.
The Caylx lasts a good year. If it needs to be touched up, it is just a matter of wiping more on the manifold. Then you get another year of a nice looking manifold.
