I have fished between corvallis and Hyatt park (watch out for guys "wrestling" in the bushes) in my uncle's driftboat. This was before I even had the slightess idea of how to catch a steelhead, and I was just throwing cranks for bass into the riprap. I only managed to catch some sqauwfish(pc is pikeminnow). I guess between harrisburg and corvallis you really need to watch for the strainers, because I heard that people get in serious trouble and get pinned against the branches and sometimes die. If fish are passing over the falls then you have a chance to hook something, but it is a wide river and kind of hard to read the water.
Good Luck