I always practiced on a gradual incline, hop on the back wheel once and drop down, and practiced rolling back as far as I could. After I was ok at that I would sping the cranks around once and got comfortable spinning out both ways. Turns out my switch spin is actually easier. At first I would lean either way I wanted and grab the rear brake sharply and let go and mash my leading pedal down and it just clicked. The biggest part for me was staying upright while going backwards and that you will need practice. Spend like 15 or 20 minutes every ride only practicing that. Do a little at the first part of the ride and a little more at the end so it doesn't really feel like practice...good luck, hope this helped...