for painting length and density just go into the particle comb mode or what ever it was again, theres the grow/cut and an option for density in there!
I’ve very impressed with the speedup and the number of hairs I can now realistically edit. However, a quick test animation shows that hairs still don’t seem to scale with distance nicely.
I’m certain the Peach team will run into that issue and fix it because they need lots of strands for grass and fur at lots of distances, I wouldn’t worry.
Did you try to enable the new distance option in the strand settings? (in the material panel).
I’ll have a go later!