That's a tough one. To avoid overheating during the trip, you should feel cold initially. But if you start with a low intensity part, it'll be difficult to warm up. And if you wear enough for the downhill, you'll be soaking wet during and after the uphill part.
I'd wear something windproof that has ventilation zippers, or remove the shell after descending before tackling the uphill part.
When you arrive to the bus stop/station, reduce clothing before locking up your bike, so you'll cool down before entering the bus.