My Scout Troop used to do a two day float down the Russian in canoes. It has been a few years, but it seems like there IS a place you can launch up by Asti - as I recall, it's a gravel beach just downstream of a bridge that crosses from River right to river left - of course I may be completely wrong with what is left of my memory. It does seem like we could drive down onto the bar.
First take-out was at a campground run by the canoe outfitter, the second da ywas at healdsburg - lot of paddling that second day.
I was lucky enough to have another adult who liked to paddle and watch me fish. I know I caught rainbows, smallmouth and "hardmouth pike" whatever those are.
That was while I was still a heathen....