Sound Proofing in Exterior, Cab, Accessories and Detailing Posted December 29, 2015 Yes the first primer is a metal primer to seal the metal or fiberglass or aluminium body panels. And yes if the lizard skin is to be painted with a top coat then a flex must be added into the top coat or as we did added to the hyfill. On the underside of the hood we sprayed the lizard sound control and then a couple of coats of green top coat to hide the dark grey lizard skin - we added flex in the top coat.Re the foam products we have not used them, we checked them out but they don't stick and seal same as the lizard skin. We have used the foam for building plumbing jobs and other general building maintenance jobs filing holes - can't compare the 2 products they are made for different uses. Old story do the homework, use the most appropriate product labor time usually about same hours, get job done properly once and don't look back.