I bit the bullet yesterday and bought a gun for use on canned insulation foam and I'm really glad I did. http://www.amazon.com/Dow-Chemical-230409-Great-Applicator/dp/B0002YOMJE I've had been using Great Stuff in a can that has the plastic applicator straw to seal up some cantilevers (overhangs) on my house; what a pain! Because its hard to control the flow of the foam from these cans you end up wasting a lot and have it fall down on you while you're working. Also, once you open one of these cans you have to use it up that day. Using the gun with the screw on cans of foam gives you much more control and you don't end up wasting near as much foam. Though the screw on cans cost more I'm pretty sure it cost me less in the end as much more of the foam went where I wanted it. Also, as long as you leave an open can on the gun you can store it partially full and use it over a month or so. I've got a lot more foaming to do as I insulate my basement and do other weatherization work. I'm actually kind of looking forward to doing the spray foam work now.