If you are getting hairs on your negatives, it must come from somewhere. Are they cat hairs, dog hairs or your hairs?

In any case, if you have the right technique, there are only a couple of opportunities for anything to get onto the negative: when loading and when shooting, i.e., when the darkslide is pulled. So, those are the places where you need to look to refine your dust-control.

If you load/unload in a changing bag, that is likely your problem. Ditch the changing bag and find somewhere with clean counter space to load.

Make doubly sure that your loading area is really clean. Vacuum your bathroom, wipe down the walls, etc. with a damp cloth and run the shower to humidify the air. Wipe off your working area.

It doesn't matter if your holders are new, vacuum them before loading anyway. I have an upholstery attachment (the rectangular brush attachment) that I've put a turn of masking tape around the brush that is dedicated to film-holder cleaning. First vacuum the outside of the holders, then pull the slides, vacuum the light traps and the inside. Insert the slide and push it past the light trap a time or two while vacuuming near it on the inside of the holder. When you're sure the holder is dust free. close the slide and stack it with other vacuumed holders. Keep them under a plastic bag so that airborne dust doesn't settle on them. Keep the vacuum out of the room if possible and make sure you use one with a Hepa filter.

When loading, wear a long-sleeved non-linty shirt. I wear a shower cap as well (the kind hotels give out for free) to keep my hair off the film. If you have facial hair, wash your face and dry with a lint-free towel and keep your head away from directly over the loading area. Wash your hands too. When loading, I always keep the film stack emulsion-side down, only turning the sheet face-up to load it into the holder. I pull the darkslide about halfway out, grab a sheet of film, turn it and load it. I quickly check to make sure the film is under the guide rails and then push the darkslide shut. Total exposure to possible dust is just a few seconds.

Loaded holders go into new Ziploc bags immediately after loading and do not come out till they are to be used.

Extend the bellows of your camera all the way and blow a time or two with the back off and the lensboard removed to make sure it's clean. If you see just a few motes of dust flying around, then you are likely okay.

When shooting, check the outside of the holders for dust, etc before inserting into the camera. Yes, I know it just came from a Ziploc bag, but... I carry a soft lipstick brush or make-up brush for brushing dust off the outside of the holders. Dust on the darkslide is what you need to get rid of. Try to let things settle down for a few seconds after inserting the holder before pulling the darkslide. Pull the darkslide slowly and carefully. Expose quickly and get the darkslide back in again. Dust that lands on the undeveloped negative after exposure is not an issue unless it stays there after processing.

When processing, make sure your area is clean and that the negs emerge from the wash and final rinse without dust, hairs, etc. on them. If so, rinse under filtered running water, mix a new final rinse of distilled water and wetting agent and soak them again. They must be spotless before you hang them to dry.

You need to dry your negs in a dust-free (hair-free) area. Clean your processing area as described above before processing. Keep doors closed and people and animals out of the drying area. If lots of stuff lands on the negs when drying, it is often next to impossible to clean them off.

The same applies to enlarging/contact printing; you need cleanliness and you need to make sure there is no dust on your neg before printing it. I use strong reading glasses and light at a glare angle from a bare bulb or the enlarger to check for dust. I use a blower to remove dust; a clean micro-fiber cloth for stubborn cases.

Do all that (it's not really that difficult) and you should reduce your problem immensely. But, with sheet film, you are bound to get the occasional black spot on the print. You need to learn how to etch, or bleach and spot these areas (or, alternately, how to retouch pinholes on the negative).

Doing all of this is the tradeoff for the other increases in image quality achieved by using larger sheet film.

BTW, I have a darkroom in the Oregon Outback / High Desert and work a lot in the Southwest deserts. My negatives are very dust-free.

Good luck,