You can buy foam in pressurized containers with hoses and a spray / mixing nozzle. It's used in new home construction. The kits can be bought at your local Home Depot or equivelant.
OR
Find a spray foam insulation contractor in your area. Take the boat to where they are working and have them spray it in.
The aresol foam it stuff won't stick. I tried.
If you refoam your gunnels, you might want to hang in some drain pipe for rigging and foam around it. You can get rigid or flexible.
Ron Pratt
Okanogan, WA
Viper/ 2.5L 200 Merc (SOLD)
1991 "the last" Virage/ 15" 280
2003 9’ Mini Virage/ 15 hp Honda 4-stroke
1989 Voyager/ 300 Promax
1989 HST / 2.5L 200 Merc
http://www.prattcustoms.com