Ed, the old method of applying laquer is to soak a cloth with it and then wipe the cloth across the work, I believe Richard St.Ledger still uses this method, I prefere to spray it on.
Thanks Phil, Leonard Bull taught me that laquer was the traditional way of preserving color case hardening, thirty yerars ago. But I never thought of using it on every day engrainving. He also said that usually the firearm would be returned to the gunmaker every year or two to be re-laquored. How often do you think one of your guns should be re-laquored?
Ed, my exhibition type guns will probably never need re-laquering because they are rarely shot, if ever.
The other guns that I engrave and that are shot will again depend on how much use they have, but they will probably be re-laquered at the same time they are serviced.