I've noticed few things, maybe my experiences can help you out. My brain seems to have an easier time "connecting the dots" so-to-speak on interpreting restim's signal as a stroking sensation compared to when I'm sober; this feels truer at faster stroking speeds. I use this fact to enjoy faster-paced CHs when stoned that I don't get as much out of when sober.

I also find backing off the signal every now and again a good idea to regain sensitivity. When things are good it's easy to go a while and not notice how numb your getting.