Getting on the Glacier Express from Interlaken

Brig is only about an hour train ride from Interlaken Ost. As enticing as the GE is especially with your Swiss Pass, I've never been on it just because it's too slow and too inconvenient. There's so much to see in Murren and the surrounding areas that the GE is only more of the same. I'd personally much rather be out and about in the beautiful scenery rather than being stuck on a slow-moving freight train.

There are two basic routes from Muerren to Lugano if you search it at www.sbb.ch, The fastest with the fewest changes is to go from Interlaken Ost to Luzern to Arth-Goldau to Lugano.
Option 2, a little bit slower with a lot more changes is Interlaken Ost to Spiez to Brig to Domodossolo to Locarno on the Centovalli train, then to Giubiasco to Lugano.
To go via the Glacier express route, (although not on the actual Glacier Express train), specify via Oberwald.
That will give you Brig to Goeschenen to Lugano. It takes about an hour longer than option 1. So Muerren to Brig follows the option 2 route, and Goeschenen to Lugano is the second half of the option 1 route.
Any of these routes will give eye-fulls of Swiss mountain scenery if the weather cooperates.
Another option for mountain scenery if you go to Brig, specify via Kandersteg. That will put you on the Loetschberg Regional train. This goes up over the mountain through the old Loetschberg Tunnel. The normal route (faster) is through the new Loetschberg Base Tunnel, so the leg from Spiez to Brig is mostly one long tunnel.

Dear Sam and Tim, thanks to both of you for your helpful "insider" train expertise! I'm not sure yet if we'll still try to ride part of the Glacier Express, but with your suggestions we'll be on very scenic train routes. Again, thanks!