Stategy/Time Efficiency

So I think I have a fairly healthy railroad set up. I currently have Bryson to Sylva Interchange, and I'm wondering what the usual strategy is to be efficient? I keep a loco in Dillsboro, one in Whitter/Ela, and one in Bryson. A fourth, my biggest, runs freight down the line.

I usually run from interchange to Dillsboro where I do my switching. Dillsboro/Sylva stuff get delivered by the local loco, which bring empties back to Dillsboro. Everything else goes west to Whittier.

While it's on its way, the Bryson and Whittier/Ela loco's collect all their empties and bring them to the old Whitter interchange. (If its a heavy load for Bryson, I'll take the mainline Loco up that way) When they meet the inbound freight, they swap, make their deliveries, and the main line loco goes back to Dillsboro, picks up empties, refuels, then runs back to the interchange.

Is this the usual "efficient" way of doing things? I haven't touched the log cars yet or done any contracts that require my own cars, and I don't run passengers, but I'd like to start both; how do I incorporate those into my daily runs?