I start 4 week old chicks with a dust bath in a tub (it's a Large size kitty litter tray.) Then a real storage tub until they're integrated with the bigs around 12 weeks.
dusty soil is great for a dust bath but even better if you add a little sand. I don't know how I got so lucky with this soil being the perfect dustbath. It's a dusty dirt, sand combo and I used to add DE and wood ash but they didn't seem to like any better than just soil and sand.
Yes, or at least I would! I don't have problems with mites because I have sandy soil. Both chicks and adults have dust baths so between their own preening and dust bathing, I think this is how they avoid mites.