Applicant discloses a two part polymer mix for use in the aircraft industry that is applied with pneumatic mix and spray gun. The two part cartridge is used in the mix and spray gun so the mix is applied immediately upon mixing, but the two components are kept separated unless the gun is applying the mix. The mix cures to form a clear sealant that allows for inspection of cracks and corrosion beneath the sealant. It cures quickly so that the coated part may be further processed, for example in the assembly line during aircraft build. Applicant further discloses multiple spray gun systems for applying such a two-part polymer mix to aircraft parts.