We have a descent amount of low brass and french horns that will be kept in the band hall over the summer months, and most of these will not be used until the start of September. These are mostly beginner model instruments. We are going to be cleaning them next week, but our question is should we oil the valves/rotors or leave them dry if they will be sitting there for a few months? Any schools of thought either way? Thank You so much in advance!