Just wanted to pass on that with the latest version of Masking in LR/ACR, with select sky, they have reached a new level of perfection. For years, masking around difficult sky subjects, like tree branches, bridges, etc. has been a real problem for me. C1 with their masking process can get there albeit with a lot more work than a single click. Example shown below. A bridge with tons of small details where the sky is intertwined, and attempting to manually mask just the sky would take hours. With Select Sky, simple single click, all the sky is selected. Create a new mask, select the sky again and invert and you have the balance of the image. Really a very good tool.
Paul