Has Ray ever mentored someone in his crazy hypnotic jazz keyboarding? I mean, is there anybody to pass his methods along, who has been taught directly by him? An apprentice?

Nope. But a lot of us try to play like him. Ray has been influenced by some many different things from boogie woogie piano to Bach. You can't really teach influence. That's what makes his playing so unique. A lot of it has to do with the keyboard bass too. Not many groups used it back then.. or now!
Dave

only some housebands in 60´s used it

or Doors tribute bands

yep

well said

I agree with that statement.

Specially because of Ray's diverse influence (latin music, classical music, rock, etc).

I'm a keyboard player. I've been doing some gigs with the tribute band Peace Frog this year. Some were in March and April but trying to learn all the bass parts and keyboard parts killed me! The band is now using bass players and I'm going to give the bass thing another shot this week. I thought I had most of these songs down reasonably well, until I really stepped up my practicing the past two months. To my shock and horror I found out even the keyboard parts on the easy songs I thought I knew, that I play every weekend, (like Love Me 2 Times) I was way off!!! Shoot! Thankfully, my next series of Peace Frog gigs kept getting postponed as it gave me more time. I work with two other bands four days a week so my time is very limited to practice. A few of the songs I'm spending well over 5 hours on. Now what was really cool was having Angelo on bass Sunday. I loved hearing and seeing him play again and watching his fingers move on those bass parts in the solo sections of Light My Fire. It was fun and getting compliments from him made all of these hours of very hard work worth it. To answer your question, I can now play like Ray, but only after working at it forever!