The back flip method is the best. Still sometimes my 3250 will double kick and start backwards. It dosn't hurt any thing just kill it and try again. Maybe by describing how I back flip will help you a little. First a good choke is needed.Usually three flips with my thumb over the carb and wide open throttle. Then three flips wide open without the thumb.(my prop in on compression when it's horizontal)
Then attach the hot shot. I am on the front side to toward the right wing so I can use my right hand. I put my thumb on the spinner and my middle finger on the top front edge of the prop. Then it's kind of like snapping your fingers. The thumb gives you leverage and the middle finger pushes the prop against the compression. It works every time. And if it kicks back your middle finger is just pushed back. Give it a try.

david