I found Bill's answer both responsive and practical as to the proportions, and reasons for using a slurry - it adds lightness.I believe you are talking about slurrying the foam. It is customary on open wet layups of foam to fill the surface with a "slurry" - equal volumes of resin and microballoons - and squeegee off as much as you can before applying glass. This has been done to make the layer of resin in the broken cells of the foam lighter than if it were straight resin.
As to paste, the terminology is usually "dry micro" - aprox 4 parts micro per one part resin. This used to fill nail holes, dents, etc prior to laying glass.
I imagine that either method provides adequate adhesion to an overlay then?
Revealing the depth of my innocent-bystander status - I also recall that some foams are dissolved in some resins - and "blue construction/insulation foam" was being advocated a while ago?