If you come to the jazz organ from a non-keyboard background (I came from playing bass), you will likely need to work on finger independence. I’ll recommend four great books for you. As you work through these books, realize that there are no shortcuts to finger independence – hard work IS the shortcut. Also, work your wall all the way through each book, even if it seems like there are easy or redundant parts.
Ernst von Donanyi – Essential Finger Exercises – This is the granddaddy of all of the books I have studied from. The first 10 exercises from the book are brutal, and indespensible for playing the jazz organ.
Hanon – The Virtuoso Pianist in 60 Exercises – Every piano student (and teacher) probably has nightmares about this ubiquitous, boring technical book. Legend has it that Herbie Hancock practiced this entire book, transposing it to every possible key. I recommend you do the same.
Willard A. Palmer – The Complete Book of Scales, Chords, Arpeggios and Cadences – You will probably look at this book and think that you probably don’t need it. Yes, you do need it, and you need to practice it until you have mastered every page.
Schmitt, Op. 16 – Preperatory Exercises For the Piano – Again, not a very sexy book. PRACTICE IT.
I really want you to succeed. Music is not a competition. The more excellent jazz organists are out there, the better it is for all of us as a community. So get serious and practice your technical skills- your helping yourself and the musical world.