I can just about do some bending of notes, but I need to learn tongue block to play old time style.
(I'm think I recently told this story here, but here goes anyway.) When I first played guitar in 1965, and all through the 70s, I tried to learn harmonica with the little instructions sheets that came with them, but I couldn't get the tongue block thing. A few years later I was working as a propman at Paramount Studios on a TV pilot starring Al Molinaro from Happy Days and Lyle Waggoner from The Carol Burnett Show. A couple of days in the producers decided the script needed a rewrite, so for the next 2 hours we sat around the set. To break the lull, Al brought out a ukulele and started singing a song, which prompted the casting director, an ex-dancer, to do a soft shoe, and Lyle pulled out a harmonica and kicked it.
As soon as they were done, I made a beeline to Lyle, and said that I've been trying to learn to play for years, but can't get it. He said he would show me the same way the person he learned from showed him. He took my hand and put the soft fleshy edge in his mouth and played it like it was a harmonica. That was all I needed, got tongue blocking then and there. I pulled out my harmonica and very quickly learned On Top of Old Smokey.
A couple weeks later I was working on another pilot, a co-costar was a young guy who heard me practice back stage during lunch. He came over, pulled out a harmonica and played some really good bending blues. I asked how he does that, he said it'a matter of pulling your tongue up and down, cupping it. I got that right away as well because when I was a kid, I'd snap my tongue really loud, which strengthened my tongue muscle and made it fairly easy to get the bending sound.