It's leg power too. Especially when running a higher gear.

Just sit on your bike, get a leg ready at like 2 or 3 o clock, lean back, pull up, and push. Once you get the wheel up it's a combination of balance and the right amount of leg power.

It's more balance than power once you learn, but to learn you will need power since that will keep your wheel up.

If you can get your hands on an older smaller bmx, easiest to catwalk on those than a bigger ike with a high gear.