The West Highland Line is not a tour that happens to use tracks. It is a working railway with a limited number of seats on the scenic sections, weather that can erase the view, and stations where the next useful train may be tomorrow. A long weekend works if you treat the train as the spine and book the sleep before the scenery.
A clean shape is Glasgow on night one, a daytime ride north, and two nights in Fort William or one night in Mallaig if you want the ferry mood more than the mountain town. Glasgow gives you a proper dinner and a station with lockers, coffee, and a clock you can trust. Do not plan to “pass through” Glasgow in ninety minutes with luggage and a lunch reservation. You will spend the ninety minutes in a queue.
Reserve the seats, then the beds
ScotRail and the Caledonian Sleeper are different products. For a weekend, daytime ScotRail is the right tool. Seat reservations on the busier summer trains are worth holding even when they are optional, especially if you want a window on the left side going north for the long views after Crianlarich. Buy the ticket when your dates are firm. The cheap advances disappear first on Fridays and on any Saturday that touches a Scottish holiday.
Fort William has more rooms and more dinner options. Mallaig is smaller, closer to the sea, and easier to get wrong: arrive without a room in July and you may be riding back. Book a cancellable room, then decide whether you want the evening in town or an early night before a morning ferry toward Skye. If Skye is the point, give it a night of its own. A day trip from Mallaig that includes a ferry both ways is a transportation project, not a visit.
What to leave off the plan
Glenfinnan looks close on a map and is crowded when a cruise-hour’s worth of coaches arrives. If you stop, go early or accept that you are there for the viaduct and then you leave. Do not stack a distillery tour with a same-day connection you cannot miss. Tasting rooms run on their own clock, and the last useful train does not wait because the tour started late.
Pack for wind even in August. The carriage is warm; the platform at Corrour is not a place to discover you only brought a city coat. And build one unplanned block — a late breakfast in Fort William, a walk that does not have a ticket — so a delay feels like weather rather than a failed itinerary.