I just bought the pedal vesion of the Hush for the exact reason you want one. It seems to work ok. It dosen't cut out all the feedback but it dose cut quite a bit out. I run it just a little less than 3/4 of the way up and before the amp. I haven't tried it in the effects loop yet. I'm sure one would get a different result going that route.
As far as the channel thing goes they might be referring to the rack mounted version. I have no experiance with that other than I use to have a
Rocktron Piranha preamp with the hush built in. Which ,btw, worked alot better than the pedal dose.