I did my first hook on a 55" vertical wall, took a bit of doin. The problem I used to have, I used to land to high up on the wall so my pedal hit the corner of the wall. But you just gotta make sure your front wheel is just on top of the wall and go slightly angled so that your foot misses the wall, and when you hit the wall, have all your weight over the bars and you'll shoot up lol. A lot of people learnin them don't go quick enough in their run up, but you gotta go faster than you think, and lot faster than a tap anyway.
Rossi.