Re: Featherfill high build primer
I haven't worked with Featherfill for 25 years so it may have changed somewhat. Featherfill was/is a polyester primer surfacer. It is great to work with as it builds fast and sands easy. It is very porous. It is essentially "spray Bondo". By contrast K36 is a urethane primer surfacer. It sands fairly well but is certainly more dense. In my opinion it's more chip resistant. The polyester tends to generate more heat from the chemical reaction with the catalyst. That makes it's more critical that the temperature of the metal is at a safe (higher) level when it's applied to avoid moisture issues under the primer.
As far as sealing prior to top coating, that will depend on the top coat and you must READ the specifics for the materials you are using. Believe me, IT MATTERS!
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