Apply gasket sealer between the gasket and the block only? or.......

If you're using a new exhaust gasket, you shouldn't apply any gasket sealer to it. It's designed to take into account some small deviations in the mounting surfaces. I'm not sure any sealant would last there anyways... it reaches temps in excess of 1000*F at the exhaust ports.

You don't use gasket sealer on the exhaust.

I have heard of using a high temp paint as a sealer, but i have never done it. - Agreed - no sealer on it. Any standard sealer will just burn up and most likely cause trouble after its burnt.

The best gasket is no gasket. If you can get a good mating surface, you can try sanding the manifolds or have them planed professionally.

Everyone else is correct, if you are worried about sealing, you could always use copper gaskets. They are soft and will conform to any small inperfection in the mating surface and can take the harsh temperature.

I have used copper RTV on the exhaust flange before, but only because my manifold flange was warped and the soft gaskets that crush still didnt offer enough flex. As far as I know, it is still on the car with no leaks and I never had a problem with it. I would only recommend that in an extreme case like mine though, just a gasket is usually sufficient.

-Joe