Blind nuts are generally a bad idea. The bolts go through the wing at an angle so that the head of the bolt is flush with the wing. The blocks are glued into the fuselage at an angle that matches the other side of the wing. If you put blind nuts in those blocks, the bolts will not align with them properly.

It's a heck of a lot easier and much better to follow the advice you've gotten and just tap the wood blocks. Take a look at this:

How to Mount a Wing