I'm currently working on insulating a van and I would like to use spray foam insulation but I'm having trouble applying it properly in the nooks of the van (specifically the ceiling crossbeams).

It is my understanding that the foam should be applied in layers in order for it to properly settle but since I can't see inside the crossbeams the only thing I can think of is to fill up the hole until I see the foam and then remove any excess once it dries but I'm not sure that's the correct way.

Are their any better ways of doing that? Thanks