I have a huge amount of time for Lee Sankey’s playing and teaching. He has produced a large number of instructional videos including a 25 part tongue blocking series on YouTube (for free!) and a superb 11 part series on Sonny Terry style country blues on Vimeo (£39, well worth it).
As if that wasn’t enough, he’s just recently released a 34 part video series on timing for blues harmonica too. I’ve yet to get to this one but I’ve no reason to doubt it continues the same attention to nuance and detail of his previous work.
If you find David Barrett’s approach to teaching a little to academic (and I know many do) you could do a lot worse than trying some of Lee’s material.
Harmonica.com recently published a great Q and A with Lee that works great as a primer for Lee’s perspective on the harmonica and contains many nuggets of wisdom.
I’ll leave you with this video of Lee playing a killer slow blues on German TV from 2004.