Can you seal up the yellow jackets nest with insulation spray?

Yes, but it probably won't do any good. Yellow jackets almost always have a second hole (an evacuation route as you might say). Even if they don't, they can burrow out a new hole and escape before the end of thier life span. Find the hole and mark it with something bright that you can see at night. After dark, approach the hole and spray a whole can of hornet killer down the hole. No more yellow jackets in the morning, guaranteed!