I have been doing this for years; I almost always separate the sky in my panos for de-noising and for excluding from sharpening. I read and tried many suggestions and found none better than I do, but that's very (very) laborous, particularly with leaves and fine branches.
First a course selection with lasso, then with magic wand the rest; with larger tolerance but contiguous at the beginning, then small tolerance, non-contiguous. Sometimes segmented, so that different tolerances can be applied.
Now, the tuning: with refine edge or modify. Do not forget to save the original selection and ADD that to the refined one, so that it only expands.
The infestation of tent caterpillars is a PITA. The fringing makes it practically impossible to select such fine structures; the transition is not sharp.
Did I say, that it is very laborous? Sometimes I spend hours on one pano for a good selection.
Btw, a perfect selection is not necessary for de-noising, but it is important, when I change the tonality, for example make the sky darker than it was originally.