I recently butchered my first Wahgi roast as well, also on the P3 profile (after a week of rest its drinkable but not standout). My roast was quite inconsistent, so Im contemplating the P5 profile (slightly lower peak power) or increasing the bean mass for the next attempt but mostly just a guess though.
My cooling method has been to hit cool at the first snaps of second crack, then open the door, pull the chaff tray and start fanning with the largest piece of cardboard I have on hand...mixed success. I have some success opening the door a crack to extend the time between 1st and 2nd crack, which would also help with seeing the bean colour
I suppose with enough experimenting, you may be able to vary the weight of beans just right to allow you to just press go and wait for it to finish. I suspect that this may not be optimum though.