Quote Originally Posted by Hexavalent View Post
Slightly de-focussing while burning in sky/clouds can alleviate grain while still adding density. This method of course does not work if razor-sharp detail in the sky is required.
That sounds like a good idea.

Usually if there is sharpness in the sky, it is due to better light and higher contrast so burning in is less likely to be needed anyway.

Your method would work on some of my negatives where I have burned in a fairly boring sky to make it (slightly) more interesting.