Usually when i do a crook i dont worry at all about the ollie or like the distance i pop from. Eventually with practice you figure out it works just like a noseslide. All the difference is:
- immediately being ready to slide on your nose (and some of your truck), but leaning back slightly to not overburden your front foot (your front foot is just a clamp, much like in a noseslide, to keep the truck and board in the position you want to achieve. you are following behind the clamp keeping the board in position and waiting for it to "drive through" the length of coping/ledge you are grinding, this is why a good bs crook kinda has a "ninja kick" look, dont be afraid to crouch a bit on it)
- making sure that your board locks in very properly, precision is half this trick but can be worked on using stalls (although they can be sort of dejecting since stalling a crook isnt very comfortable to stand on without parallel momentum)
- making sure your weight once you lock in is perfectly balanced between the ball of your foot and your HEEL, this very much seems at first like you have to transfer ALL your weight to your front heel to keep the pinch clamped tight but this isnt very good for when you need to pop out or end up catching a bit on the ledge (need to be able to adjust that clamp for certain obstacles)
Right now im learning switch crooks and im trying to use these same principles, but the eluding factor still remains with me clamping my heel too tightly, getting a good grind and pinch, but not being dextrous enough to transfer my weight to the ball of my foot slightly, pop out, and keep my shoulders parallel enough through all that to ride away comfortably switch. The one thing that does help though is imagining my front foot as a clamp and sort of bulldozing behind it as i use it to grind one tiny corner of my truck on the ledge.