Sean, thanks for jumping in and answering John's questions. About choosing the right foam, I intentionally avoided the open cell vs. closed cell foam debate. I did this partly because it's worthy of an article all by itself, but mainly I didn't include it because, despite all the warnings the two sides issue about the other, I've never personally seen a problem caused by using open cell where they should've used closed cell or vice versa. I'm sure things like that happen; I just haven't seen it yet.
Allison--would be very interested in your take on the GHG issues of foams, which have received lots of smart commentary recently. To highlight a few: architect Jesse Thompson's comments on Tom's Good vs Bad post on Energy Circle, the very thorough piece by Alex Wilson on Green Building Advisor and Michael Anschel's cautionary diatribe on Remodeling. 

A: It can be applied in the similar manner that we apply paint. We can use a paint roller to apply it without any hassle and use of special tools. You can also check the specific manual of instructions from the maker for particular directions. You should also check if it requires single or double coating or the use of a primer before its application.

Spray Foam Attic Ceiling

When choosing a waterproofing and sealing product, we must see to it that we can easily use and apply it using simple tools, including a squeegee or a paint roller. With ease of application, we can be certain that we can achieve hassle-free application and smoother and more attractive finish than other products could give. So when reviewing the products we have featured above, we have made sure that they are easy to apply.

Roof Coating