I haven't fished it either, but I've ridden Smith River Rd numerous times and it seems like the upper stretches between Spencer's creek and Sisters Creek have decent access, at least in the sense that the road is near the river and it's public land. Via Google Maps, it looks like bank access would be limited below Spencer's Cr, but there are a few spots I can see from the map. Bigger question is what to fish for. Below Spencer's Cr the river is open for hatchery steelhead year round and Chinook Jul1-Nov30. Same with the North fork. Above Spencer's it's open during regular steelhead season. To my knowledge, there aren't fish any being planted in the system and it's being managed for wild stocks. If that's the case, all one could really hope for would be a hatchery fish that took a wrong turn.