How to deal with the mess when working with Tuff-R
Tuff-R is polyisocyanurate foam.

For styrofoam (polystyrene) using a hot wire cutter to melt rather than crumb the foam is less messy, though with more fumes/smoke. You probably don't want to try that with polyisocyanurate, since the fumes given off by it are far more toxic, per a brief search.

For any sort of foam being cut (sawn) to crumbs(some types don't melt), vacuuming while cutting is helpful.

If you can make your cuts with a razor knife or similar non-crumbing tool rather than a saw, that can help, but may require more effort to make the cut.