can anyone help
Just a thought… Have you tried the track brushes at all? Can find them in Lightbox>Brush>Tracks.
Track2B.ZBP or Track2.ZBP might help you, obviously changing to your desired alpha. I noticed in your vid that you had several lines in your alpha. Maybe reducing the lines to just one, whilst using the track brush with lazymouse on and playing with the steps may get you a little closer to what you are trying to achieve.
Hope that helps. Not got Zbrush on the system I’m using at the mo, so can’t test it.