This lesson in how to play modes is maybe the most valuable giveaway I can give to my many followers. Once I discovered this little trick, I found it strange that nobody had shown me this before.
The idea is to see the modes as just diatonic scales and practice all the modes systematically in all keys. This requires you to only practice the 12 diatonic scales, and not 12 x 7 modes.
This is my video from YouTube on how to play walking bass lines (jazz piano):