Different expanding foams have different densities, and some of them end up curing very porous - this has the problem of soaking up thinner paints and such.
I had a batch in the past that was so porous, that all my thin paint kept getting sucked up - I had to paint over with a thick, latex paint (some drywall primer) to seal the surface. I was then able to paint without trouble.
I use red metallic spray paint, then once dry add a top coat of glue blood (Stiltbeast formula). The glue blood dries with a wet look to it, and is far better than any of the store bought bloods. It is clear Elmer's school glue with several drops of red food coloring and a single drop of blue food coloring.