Resetting Painter
When Painter starts acting weird, shut it down and restart it while holding down the shift key. You'll be asked "Current Workspace" or "All Workspaces", choose either one and click OK.
Painter has lots of "gotchas!", as in you do a certain thing in Painter and "gotcha!", Painter explodes, craches, corrupts files, melts your tablet stylus... you name it. This is a list of some of the more cantankerous gotcha's and how to work around them.
If Painter's Brushes are running really slow
If Painter's brushes are running really slow, as in there's a significant lag between moving the brush with the tablet cursor and the brush on-screen responding, go to the Preferences menu under Interface, and turn off "Enhanced Brush Ghost", and set it to any of the other options
Using the Scroll Wheel to Scroll and not Zoom
If you hate that the scroll wheel doesn't scroll, but instead zooms in and out, hold down the command key while scrolling to scroll up and down, and the option key while scrolling to scroll left and right