I have to give credit to the local hardware store owner as this was his idea. I wanted to foam around the windows in the new house but my foam gun barrel was too large to get into the areas that needed the foam.
I have a cheap model which dosen’t have the small tip option.
Solution – electrical heat shrink tubing. I just cut it to length, put it over the barbed end of the gun barrel and placed a smooth 16 penny nail in the end and then heated. I did find that I needed to secure the portion on the barbs with the small wire from a twist tie. Worked great as it stays flexible and will even flatten a bit to get into some very small cracks. I also used it to secure a small straw to the gun to get into the 5 1/2″ areas around the doors.