I fish surface flies 80-90% of the time for summer steelhead, and I am always using riffle hitched hair flies. I've had the fish take the fly seemingly every way imaginable--sips, head-and-tail, explosions, follows and grabs, and wait until it passes and chase it downstream like a torpedo. So, I don't think one can generalize about how steelhead take a waking fly; Atlantic salmon may be different.
I hitch like Lee, but I have the leader come off the bottom. Since I'm fishing hair flies, the profile is already significant, but I'll still vary the size of fly depending on water depth and speed. I'm not certain if that matters, but I'm pretty convinced that having smaller flies to follow-up to a "player" is very helpful.