Have you tried transcribing the bass players lines for Oleo (or other rhythm changes tunes?). IMHO and experience that would probably be the best place to start. I transcribed Paul Chambers line on Miles Davis's Relaxin' Oleo, and he plays the hippest line I've ever heard and for me, that was the best way I learned how to play the rhythm changes.
But I mean, not just for Oleo, or rhythm changes, but for a lot of tunes, I guess transcribing, or playing what the pros play is probably the best starting point to learn how to approach a tune, so then after you've learned and memorized their line note for note, you'll naturally start changing their line, playing a different note here or there, adding a skip or a drop, until it becomes part of your vocabulary.
thats just my 2 cents, I hope that helps.