Yes, dry mounting is a craft unto itself. I can still find ways to screw it up, and potential problems multiply with increased size of print. Perhaps it is an adhesive you are after, for the posters.

Also, for larger stuff like posters, you can only get one overmat from a 32"X40 matboard. The most economical is 16X20 mounts (say for 11X14 prints) as you can get 4 overmats from a single sheet.

I don't know if you cut your own mats. Something to consider, you get to keep the cut-out pieces for other uses. Mat cutting is also a craft in itself, and necessitates some period of frequent failures.