On the two rifles I have the actual frizzen pan seals so tight that if I hold it up to the light, I can make out no light under the frizzen lid. Snow seal would only be messy in a case like that. If you want to smear snow seal, or candle wax along the edge, it should not hurt anything.

A friend of mine puts a simple baggie (for sandwiches) over the lock and frizzen and then tucks the how mess under his arm. When he is ready to shoot he pulls the baggie off and cuts loose.

If you want to stay traditional, as your signature suggests, I wouldperhaps look into a leather cow knee. Get it well oiled and it should keep the lock dry. Change your prime every sooften, and youshould be fine.