B-12 functions as a stimulant for roots, it is very beneficial for transplanting anything, it also does stimulate rooting of sicon stock being rooted.
Yes I would carefully rinse the clay away until you can see if any roots are forming.
If they aren't I'd score the bark and soak in some willow water or use rootone for really aggressive rooting action.
Hazelnut roots fairly well if first year
wood is used for propagation. I have done some using willow water as the rooting medium then watered in with a mix of B-12 and willow water. This method works fairly well.
For most rooting of difficult to propagate plants, trees, bushes, I use a 6% Rooting powder, this is a commercial nursery item, the Rootone you can buy at places like walmart is only 3%.