The product your talking about is using a straw application, but it can also be emitted as an airborne spray. The foamy worm stuff seems better suited to filling voids, whereas the spray is made for open surfaces (like roofs).

I can imagine applications for both, but I'll start with the spray on first for the shelter and then we can experiment from there.

I am hoping that once I build the shelter, spray it down, and let it cure out, the foam will be rigid and sturdy enough that I could uproot the little hut and take it with me to relocate.

Hmmm, that may not work so well, but I have some ideas on that too...