I can't do grab from b1 consistently to save my life.So far, all you can Get B1 into grab fron a low shot is either on its own, or from a standing 1. I haven't found any other ways to get it, the opponent is pushed too far back, it has to literally be right in their face or grab = Nobo.
I've been doing (upclose)
low shot --> d1 --> grab --> b3, j2, 21 bf3)
much easier to confirm grab from d1 and damage is the same I think