Here's a video by a linguist / harmonica player, Carl J. Weber, that describes and demonstrates how to overbend using formants, which he defines as "silent vowel" mouth shapes.
Interesting viewpoint from a lip pursing perspective though not sure this will be helpful for tongue blockers?
It will be interesting to see if this approach will be the breakthrough for folk who haven't been able to do them. As someone who can already overbend I have followed the instructions and it seems to make some sense.
Half the battle though when trying to OB is visuaising the overblow note so that you know the note you are aiming for.
Whistling the pitch of say the 6 blow will not of course be the note pitch of the 6OB, it will be higher.
I take it that the overdraw method is to do a backward whistle. I noticed he couldn't really sound these whistled notes but he must have been shaping his mouth to whistle these high notes esp in the case of hole 10. ----------
