My 2 cents say that the blanka matchup is 5-5. Neither character has a safe approach. Both characters can be punished on blocked specials with ultra 1. It really comes down to who can be more patient. Noone is getting damage in this matchup unless they punish or take a risk.
In regards to punishing blanka balls with u1, you have to wait a second or so before punishing. If you do it right away and you get a reversal, you’ll likely only get the first 3 hits. You have to hit blanka after he lands, but before he recovers, which is like a 2-3 frame window.
I’m not sure if it’s been posted before, but i feel it’s important to note that t hawk’s condor dive can be punished with u1 as well. It’s like honda’s fierce headbutt, in that you can do it asap, and it’ll hit fully every time.