Primer sealant, intended mainly to keep gun oil or cleaning fluid (e.g. Hoppes) from ruining the primer, is nothing more than lacquer, which for practical purposes is the same as nail polish. Modern factory ammo is sealed at the primer, but, except for military contract, not sealed at the case mouth.
If desired, and for reloads, a drop of fingernail polish at the primer pocket and a swipe with the brush around the case mouth will seal the ammo with no problem.
Another suggestion, if a fast draw is not going to be needed, is to drop the loaded gun in a zip-lock bag. That will protect the gun and ammo and if necessary the gun can be fired through the bag. A revolver is better for that, though, as the bag may interfere with slide movement.