It is best to prep and coat the outside of the frame first allowing the RustSeal to fully cure at least 24 hours before applying the Cavity Coater to the inside of the frame. Doing it this way allows you to easily wipe off with mineral spirits the Cavity Coater if some of the Cavity Coater comes out of the holes of the frame.
Before you start you restoration, check out the RustSeal Directions and the Cavity Coater Directions.