Ok, if you like to paint using adobe photoshop + tablet combination, here are the shortcuts to be know:
Hold R + moves pen while clicking = rotate the canvas, pretty useful if you can easily do some movements in one way, but have trouble doing in some other direction.
type H = pan the canvas so you can paint a different area
type B = select the brush tool, which pretty much is the same as get back to drawing mode
Ctrl + Alt + Z = goes back a history item
Ctrl + Shif + Z = goes forward in history
Ctrl + A = selects all (type Del to delete everything in a layer)
Ctrl + D = de-selects all
Also, to increase productivity, I draw with as m