I like the Mastic.
The only issue would be if you did not like getting your fingers messy.
(cleans up MUCH easier than Great Stuff)
I used a utility brush from the paint department for spreading it around. It was the closest thing I could find to what the A/C crew was using.
I have not found it in all of the big box stores, I had to keep my eye open.
I always keep a list of things to look for when I visit another city too.