I never though of notching the post.
I take a piece of scrap 2x4 or whatever I have lying around, and screw it into the side of the post. Same result, just probably takes a little longer.
If you don't have a
FEL or tractor handy, you can also do this towards the bottom of the post and use a hydraulic bottle jack to get the post out. I've done this allot when repairing fences.
Eddie