Just read this informative article by John Paul Caponigro on creating gradient masks. Written for photoshop, I think the same techniques would apply to PE as well. While I can't say that I have a handle on all that he explains I thought it was worth sharing.
Canon 7D MarkII Lenses....24-105 (my newest and I love it), 10-24, 50mm, 70-300, 17-55 Sony NEX 7 Lenses...10-18, 18-55, 55-210 NIK Suite OnOne Photo 10 Topaz: Adjust, Clarity, Simplify, Clean, Lens Effects, Remask, Impression, Star Effect, Restyle and DeNoise
Great read, thanks very much Helen for pointing the article out to us. Given how powerful they are I really must make an effort to incorporate them into some of my images. I am going to have a bit of a play with the this weekend (time permitting).