It is hard to find a good video tutorial for the pistol squat. I think this one by Al Kavadlo is pretty good. Nice progressive exercises, though I wonder if it is possible to get the straight leg at a more perpendicular angle to the ground?
I’ve been working this exercise (and the handstand) this week, with minimal progress. Ramping up my miles, and doing a bunch of body weight squats has destroyed my legs. Gotta get sore before you get strong I guess.