Excellent ideas, especially the Ballistol & hairdryer.
A word of caution, you have no idea what is in the horn: maybe nothing, or maybe some black powder, or bugs or .... Just because it doesn't feel heavy, or just because you can't hear anything when you shake it, it not proof it is empty. Even a few grains exploding could wreck your career as a brain surgeon or concert violinist, or any occupation that requires five functioning fingers on at least one hand.
Treat the horn as if it contains black powder! Carefull with the hairdryer.