I finally got the details of the wall run right, I think. Okay, at a very modest hight (garage roof) and I skip the topout because people tend to be cranky if they see someone climb on top of their garages. (Jumping up at a ledge earns you enough suspicious looks though once you tell them it's for training I've had no problems.)

Anyway, I figured out an important piece of the puzzle which I'd not considered so far, which is that I need to focus my attention entirely on hitting the wall with my foot, and completely ignore the grabbing the ledge part because that's an automatism anyway. Once I started to really focus on the proper spot on the wall while running at it, it became much easier.

But I'm never gonna manage the parkour-style topout... way too difficult. I prefer the climber's style where you get your heel on the ledge and haul your body over. Not as elegant but hey, whatever works. :)