I like to leave Eburg, head West and then turn around at the old homestead just beyond the first tunnel. I bring a flash light or compact head light, as the tunnel is long enough that it is very dark in the middle. You get the slight incline of the old rail bed, the sights of the river and the safety of a trail.
It's best on either a wide tired road bike, a fat tired cyclocross ( I use 38c) or a slick equipped MTB. I have hit 20 mph on the gravel with a slight wind at my back. I felt safe doing so, as the gravel can be an ok surface. Hopefully one day the trail can be paved like the trails in Bend or Coeur d'Alene.
No water on the trail, but there is water at the Thorp fruit stand.
Expect to see very few fellow cyclists (You'll see more fly-fishers on the river in fact)
Take your spare tube and a patch kit. It's lonesome out there.