Fiberglass - Melts Styrofoam, you need to seal the foam to be able to lay fiberglass.
Successfull sealers :
Epoxy Resin - Ideal for styrofoam and wont melt anything. Can be used as a sealer for fiberglass, or to be used with fiberglass cloth and be used for the hull without fiberglass, but it is not as strong as fiberglass.
Rust Destroyer - It is an automotive rust primer, seals the styrofoam partly, put two light coats of Tremclad paint and then put some fiberglass.
Masking Tape - Cover the foam with the tape and is seals the styrofoam, good for a flat surface.
Products which failed :
Latex Primer - Wont melt foam but does not seal styrofoam.
Rubberized Asphalt Undercoating - Wont melt foam, gives a nice finish but does not harden completely. Does not seal styrofoam.
Rubberized Rockguard - Melts styrofoam fast.
Automotive Primer - Melts styrofoam fast, but good to put on fiberglass to obtain a smooth finish.
Elmers Spray Adhesive- Wont melt foam, good to bond parts together, but it does not seal the styrofoam well.
Water Base Acrylic - Wont melt styrofoam, does not seal the styrofoam.