Best way to hold XPS to wall while adhesive dries?

Guys, I'm currently applying 2" Owens Corning Foamular 150 rigid foam to my basement walls. All the foam has been cut and dry fit and now I'm ready to attach. I purchased Loctite PL-300 foam adhesive but I'm having a hard time getting the foam board to sit tightly against the wall. My walls are poured concrete so they aren't perfectly smooth. Any ideas?