I use a big clip (plastic Chip Clip or similar) on the body of the siphon to keep it from going down further than I want so I don't have to hold it. I put it in at first so it is about three inches from the bottom. That's well above the trub. I fine tune slowly and carefully as the volume drops to keep the black tip just below the surface.
When I racked my ESB this way into my secondary, I got a bit of trub, but it was mainly stuff that was suspended in the beer. It settled out in secondary. When I racked into my bottling bucket, I didn't get any of the 1/2 inch of stuff in the bottom of my carboy into my bottling bucket. My beer looks really good.