OOh oOh ooh...something I can answer finally.
Ok usually when I am done using can of said foam I unscrew the straw and trigger, and blow that out with air from my compressor. That takes care of the straw. As for the can I either do like CraigFL said , or I put a little cap for wire shelving on teh end of the nozzle.
Now then. If I happen to forget to do any of the above, I go to my parts bin, adn get a fine thread drywall screw 1.5-2in in length. Thread the screw down the end of the straw at least half way. Then easily tug, adn usually the dried foam will come out in one long chunk. Anything that is left is wet, and can be blown out with the air.
Works for me. Try it for yourself.