Well back in the day it was painful trying everything for myself and watching videos of the grandmasters to see if I can get what they are doing…
Nowadays:
We have our controller scratch course coming next year, this will be the first course aimed solely at scratching with controllers. So that is for the people that want to stay fully digital.
Apart from that DJ Angelo has a nice series on youtube (just search for DJ Angelo) explaining turntablism really well in several lessons. He does it using a standard turntable setup, but of course you can translate many things to controllers.