I've been trying to use the brush too for awhile now although it's not working. For the most part i use presets, and when tring to brush over something to lower exposure and use the overlay to see where it effects nothing shows. I've been trying to research the issue although i've found to my knowledge no one else having this issue. If anyone has ideas to what could be going wrong my ears are open.
Yeah, the colour overlay doesn’t appear after I’ve brushed and I even try to change the exposure or contrast. Anything that would make a visible difference but nothing shows. Thinking of uninstalling and reinstalling. Been faulty for myself since the new update with the masking feature.