Oh man I had a hard time learning these and I think I had the same problem you did. The number one advice I can give you is to NOT look at the end of the rail as you set your spin. Wind up on the rail - almost as if you are hugging a barrel - and have your front edge set. From there pop and keep your head looking over your shoulder, not at the ground. I posted a thread asking for help last year and there is some good advice on that one.
I would say the best place to try them would be a flat tube that has a decent sized drop, but if the up rail works go for it