TB2 (Titebond II) is your best friend. Buy it by the gallon. I have used it for virtually all of my wood to wood joints and some of my wood to foam joints (on foam to wood just use a thin film with no big drops, streaks or puddles... roll it on big flat surfaces or use old plastic credit/membership cards as scrappers... otherwise it might not dry well; you need a nice tight dry fit, too, because it does not expand). It worked good on machined joints in foam (i.e. router pockets for wood blocking), but I would not recommend it for rougher cuts or "sorta" flat areas that have been roughly sanded.
I used GG (Gorilla Glue) for all of my foam to foam butt joints and most of my recessed/inset blocking, however, it squeezes out (not always, but often) and cures harder than the foam board making it difficult to sand w/o gouging the foam. For this reason I am going to try using GS (Great Stuff) for my remaining foam work. From what I gather the trick is to knock it down so it doesn't foam so much. Also, use a drop or two of acetone (with disposable rubber gloves) to clean the spray can tip and straw; works marvelously and saves the rest of the can. I was reluctant to use it in the beginning (until I learned the acetone trick) then used it to patch a small hole in my wall; it sanded so much easier than GG because it was softer... maybe not as strong (
).
I used the 3M 30NF green water based contact adhesive, but I don't think I would recommend it due to the cost, and I'm unsure about the performance (some areas of foam to ply that I cut out later seemed to pop apart too easily for my taste, whereas the test piece that I did with rolled on TB2, scuffed blue foam and either Okoume ply or pine could not be separated). I think as long as the joint is not so wet that the wood can not absorb all of the water content, and the joint is tight, TB2 works great for foam to wood. My guess is that the people who have had problems with the glue not curing had used too much glue or had brush streaks and pooling... or maybe it was climate related.
I would
not use TB2 to join foam to foam.
I have also used the TB2 as a sealer coat on the underside of my floor (which will also get painted later).
I did use a little Bondo as filler in a couple of spots, not much.
That's it.
