I recommend the ex SP&S mainline through Finley. Highway 397 parallels much of it and there are a whole bunch of crossings if you are shooting video and want some good horn sounds. Cross the Columbia river on the cable bridge and continue south on Chemical. If you are there towards late afternoon you might catch The Gunderson switcher working the BNSF interchange. Go left (east) on Cochran; about 1/4 mile south of the General Store truck stop and go to the railroad crossing. Here are a couple of videos of the Gunderson switchers:
GE 45 ton centercab
GE 65 ton centercab