I think you probs need to set opacity to pen pressure and if you already did that then lower the opacity to like 50% or less to get a better gradient.. then when u go over it multiple times, it builds up (i'm also a CSP user)
setting opacity to pen pressure should mainly do it tho. u just need to practice controlling the pen pressure
I made a thing for u
here's how i did it - apparently it took me about 12 mins but yea its all about the pen pressure - sometimes u need to build over each stroke and smooth things out
I probs could have made it smoother if i spent even more time on it
(its not showing a thumbnail cuz its unlisted but the vid should work.. also its for some reason taking forever to render in HD - says about 40 mins left but hope it helps!)