Does anyone know what trains to take from Lauterbrunnen to Lake Oeschinen to ride the mountain coaster there?
Lauterbrunnen to Interlaken Ost to Spiez to Kandersteg, then the 242 bus to the lift station.
For this and any other transportation question, you can use www.SBB.ch/en. There is a handy app, as well, which is very nice while traveling as you can buy tickets with it. SBB planning includes all trains, buses, boats and gondolas or other lifts.
If you want to experience a mountain coaster there is one in Grindelwald as well. See Pfingstegg.