One of the oil finishes on about 65% of my calls, about 20% with a spar finish and the last 15% anything and everything in finishes that are available. I mainly use domestic hardwoods so any finish will work, I use what I think is best for the calls that I am making at the time. For some customers, the finish is decided by the customer, for other customers I know how they treat their calls so I use the finish I think is best for them.
I also wax and buff each call before they are sent to customers. I try to explain the need for wax, but a lot of times it falls on deaf ears. Some listen, but I have seen some calls come back for new reeds that look like they have been drug behind a pickup for a couple of weeks. Those usually get cleaned up, and I give it a oil finish with a coat of spar.
Marvin