The better bulk loaders don't touch the film when the light trap is open. Having said that I have some 35mm cassettes from 20 years ago with over 20 loads on them and they still work fine, so I suspect you can get good results from a felt-trap in a bulk loader. I'd vacuum the trap well. What type do you have?
In general 35mm bulk film gets wiped once in to the cassette and once on the way out, and I can't recall ever having dust on a 35mm frame. If you are using a vintage 35mm camera, make sure there is no dust in the mirror box.