If ever there were a more difficult way to catch a steelhead it would IMHO be with a fly rod. But that's just me and I only hold that belief for steelhead. That said I have found steelhead holding with tight lips where you could see them. Cast a fly and mend right into the 'feeding line' and the fish would just move slightly to the side of the offering. Rest the hole a half hour, (about the time it takes to drink a beer!). Now ROCK the hole above and the side of the fish. Immediately after you ROCK the hole cast and do exatly what you did before and more often than not you'll hook a steelhead on the first drift through. I've done it, it has worked for me so I'm pretty sure the sled does the same thing.

Additionally I've run my sled up and down a hole where we just had a bite and pulled as many as three fish out on the next run through, not five minutes after we ran right by them.