Apr 27, 2017 - 2:19 PM
Hi sydneyjen, welcome to MySwissAlps!
Yes, the route via Locarno-Domodossola-Brig would be great. You'll travel over the Centovalli line, a beautiful, romantic route that crosses many forested valleys. You may spend the night in Brig and make a side trip to Zermatt the next day before moving on to Interlaken, or simply spend the night in Zermatt. From Brig/Zermatt you'd best catch the regional train via Goppenstein to Frutigen, Spiez and Interlaken. Note to enter Goppenstein as a via-station in the timetable at myswissalps.com/timeta ble when looking for connections; otherwise it will only display the most direct route crossing a long tunnel and you'll miss out on the beautiful views.
Alternatively you can catch the Gotthard Panorama Express from Lugano to Lucerne and then movo on to Interlaken, but since you've already visited Lucerne this may be less interesting to you.
Once your plans are more or less set I advise you look into rail passes to help you save money: myswissalps.com/train/ ticketspasses/practica l/chooserailpass.