Howdy Group,
When I'm gluing my built up handles for board bows, I use TB2 or TB3.
I usually rough up the surfaces with 60 grit, and then I'll do a really good job of cleaning that surfaces using acetone to remove dust and, mostly, to remove oils on the surfaces. (Then let it dry completely - about 1/2 hour.)
I make sure to put a thin layer of glue on both surfaces.
When clamping, I don't go real tight, I just clamp the wood snuggly - so to not cause any dry spots; (where all the glue had been squeezed out).
I learned this method on PA, and it works for me. But, Justin knows his stuff, so if he says use 120 grit - use 120 grit.
All the Best,
Canoe