controlling your height on wallshots depends on your speed, and your aim according to your speed. The slower your horizontal velocity the easier it is to continually gain height. If you wanna wallshot at the same height over a long distance, you need to maintain a constant speed to assure your rockets will stay enough under you to still give you height while not gaining too much speed. Learning how to do anything in jumping simply comes from playing a lot and figuring out what you're doing wrong through trial and error. So just practice a bunch and you'll get it in time.
