You can brush straight lines with the adjustment brush -- rather than holding the mouse down, click where the line should start, and then shift-click where it should end. Each time you shift click, it draws a straight line from where you last brushed.
For windows, for example, I often select a low value for Feather and Automask, then straight-line brush the edges of the window. Then with Automask turned off, I fill in the window. When Automask doesn't work as well, I'll brush a straight line without it. Here's a video: Dropbox - straight-lines-adjustment-brush.2019.03.01.mov