My exercises:
Make it more musical than mechanical -- sounding like you're playing exercises when you think it's musical comes when skipping intermediate steps. The next step after this is polymeric hand over foot ostinaotos, like double bass/latin feet in five or seven against like some Indian rhythm in three or four on the hands. Patience. Use a metronome and develop the Mueller technique. Play it in swung time, too.
https://docdro.id/tAzE56z