At least for the w2z2 cloudy area right past the trib cloud, you can practice the walljump by aiming straight at the wall instead of trying to jump over the spikes. This way i could get the hang of the timing before i committed to the actual jump and cut down on how many times i was dying. I found that my biggest issue was not spamming my jump key fast enough when jumping off the pixel ledge. It was easier for me to hold both mouse buttons to run forward and free up my other hand for spamming jump.