Deck hardware hole file without access to back side.

[Disailor]

With regard to canned foam. I leave the ball of foam at the end of the straw to solidify (watch out for drips). Since the foam cures with moisture the ball will seal most of the tube & the nozzle.
To re-use simply pull/pry off the end ball, remove straw from nozzle & carefully push a straightened coat hanger wire thru & push out the foam. If the foam has hardened fully then squeezing the straw with pliers will break the bond between foam & straw & you can push it out with the wire. I've successfuly re-used canned foam weeks after initial use.
If the foam has hardened into the nozzle. A sheet rock screw carefully (!) inserted into the foam & pulled out with pliers usuall works.