Welcome to the party !!! You've gotten some solid advice so far. Cleanliness is really important to processing. B&W processing is really straightforward for film or prints and really enjoyable too. But when you've got to combat dust, insulation and grit falling into trays or processing equipment or blowing in the wind it becomes a real battle.
So, what I suggest is that you go down to some home center or lumberyard and score a roll of 6mil visquine plastic in either black or translucent. (Black might allow you to work in the daytime) It's pretty heavy duty and should handle large construction staples well. Try and confine a small area of your garage and enclose it, ceiling and sides too. Slit a doorway flap in it so you've basically built a tent and use an air purifier / cleaner inside along with a small fan to move air. Ventilation is important while you're working.
You can even make a film drying area inside a small hanging plastic frame (like PVC pipe) with a plastic sheeting for sides, kind of like a narrow vertical tent. Oh, and when you wash film, don't forget hypo clearing agent AND photo flo to prevent streaks and curling of your negs.
After you get it all cleaned up as best you can, vacuumed and dusted, keep your equipment clean and maybe stored with plastic sheet covers over work surfaces. You'll be much happier for it and your work will really benefit.
I've processed and printed film in all sorts of terrible work environments from motel bathrooms to tents. Dust and dirt is the enemy. Minimizing it really helps the enjoyment and productive level.