Splurge on a Gun—You Won't Regret It
If you've got more than a few windows or doors to seal with foam or are planning to make the whole house airtight, you should consider investing in a gun to dispense the foam. A basic model like the one shown here costs about $30. Guns have several advantages over cans with plastic straw applicators. First, turning the knob on the back adjusts the flow rate, so you can dial in the size of the foam bead to match the project. The long, rigid tip gives you better control and access, especially with the added disposable tip attached.
When you're done using the foam for the day, just wipe off the tip and set the whole works aside. A ball in the tip seals in the foam so it won't cure in the gun. You can leave it like this for up to a month without cleaning. When you do want to clean up the gun, buy a can of cleaner, screw it on, and spray until the gun is clean. You can also buy cans of urethane adhesive and use the gun to apply it.