+1 for Topaz Remask3, but view some of the tutorials on youtube before you try it on a really difficult picture.
Topaz seems to be a company that has done a lot of innovation in their approach to processing. While they have a large number of plugins now that may seem to overlap, and which can produce really grungy effects, they are easy to tame and use for very subtle effects, perhaps with fewer artifacts than NIK, which I also love. Remask and Denoise are superb.