Been using the tool quite a lot recently and there are quite a few issues with the way it works right now.
The first issue is that the brush disappears as soon as you start applying vertex paint, once you hit the mouse button the brush disappears and you can’t see where you’re applying the paint until you see the effects of it. Probably a simple fix for this I would have thought?
The second issue might simply be caused by the first, but I can’t tell, but the tool doesn’t seem to apply paint uniformly across the surface, some vertices will get a much more intense douse of the tool than others. UE3 seemed to paint much cleaner and more intuitively than UE4 so far.