Stratmosphere had those brushes last winter IIRC. I got mine a long time ago and like them, but I don't use the brush on anything except my glass. Just not soft enough for me.
IMO there's no way to avoid the risk of some light marring if the car gets really covered with snow. Just the melted stuff sliding across the paint can mar it if the snow contains any abrasive grit. The method White95Max described (clearing off all but a thin layer) are about the best you can do. Keeping a healthy layer of slick LSP sure won't hurt though.
Oh, and those Sno-Broom things work OK for this, but if you use them to really clear the snow off, as opposed to leaving a thin layer, they'll mar for sure. Still use mine on rentals though
