I used the Sno Brum, VERY carefully, on the Volvo (soft single-stage) and yep, I got some marring. On THAT car, I wasn't too upset, I just polished it again in the Spring. If there's abrasive dirt in the snow, or between the snow and your paint, and you push it across your paint, you're gonna mar the finish. The Volvo's original owner would "wash" it in the winter by pushing the snow off, and some of the marring from THAT will only come out with a paint gun.
IMO, the only TRULY safe way to clear snow from painted surfaces is to leave a layer of snow ON the paint, so there's no direct abrasion going on against your finish. Even then, when/if the snow melts and slides across the paint, well, that can mar it too.
For clearing windows, I got a scraper/brush combo from Stratmosphere (sorry, I don't have a link handy). The brush's bristles were boar's hair, so if you accidentally touch the paint with them while clearing the glass you get a narrow margin of error, at least more than PLASTIC bristles give you.
Oh, and DO be careful when you clear your glass. SO many cars have scratched up windows from careless scraping.