The video demonstrates sealing a window with Flex Caulk, a hybrid formula that's 100% weatherproof, doesn't require a caulk gun, and can be painted over (though it's clear enough you won't need to).

Key Steps:

1. Prep the surface - Clean around the window perimeter with denatured alcohol (or soapy water if there are decals nearby)
2. Important warning - Never seal the weep holes at the very bottom of the window frame. These factory holes let moisture drain out - sealing them causes water buildup and bigger problems
3. Application - Uses the snap-and-save cap with trigger flow nozzle that adjusts product flow left/right. Start on full power to clear the valve, then apply using the "start low and go slow" technique around the perimeter (stopping before the bottom weep holes)
4. Finishing - Smooth the caulk with either the Flex Gap Filler tool or your finger, then wipe off excess