Logistically, Missoula is an easy place to start a tour for me. I can fly to MSO from the east coast and take a short taxi ride to the pretty quiet KOA on the west end of town. I ship my bike to REI, which is a two block walk from the KOA, and it's ready to ride when I arrive. REI holds my bike box and duffle bag and I pick up fuel for the stove and any last minute items I may need. The next morning I shove off. When I finish, I drop the bike off at REI, give them the shipping documents, pick up my duffel bag and go have a beer.
In terms of meeting people, the first two days and some of day three follow the popular Trans Am route. After a detour off that route you rejoin it at Twin Bridges and take it for another day to Ennis before leaving it for good. From there, you end up on the L&C for a bit. Last time I rode out that way I encountered at least a dozen people doing the Trans Am or L&C and I didn't do the mileage to Ennis that year. This year my penultimate night on the road will be spent in a town where ACA's Cycle Montana supported tour will be staying.
Send me a PM if would like details, including a route map with elevation profile.