HI Gwen and welcome to the Forum :wave:
Diatomaceous Earth is an old remedy, and probably quite effective, but it can be quite damaging if inhaled. Not something I would dust over a pet, but you may have had advice to do so?
So for Cheyletiella mites, as others have said, the treatment is Ivermectin. Given to all rabbits in contact with each other, and the dose repeated at two weekly intervals for three doses. It's usually given as a spot on treatment these days.
Please don't bath your rabbit! The shampoos are not guaranteed to work on rabbits and bathing is very stressful for rabbits.
You can by an over the counter spot on, called Xeno, but you will need the weight of the rabbit and your vet can more correctly identify the dosage:
http://www.medirabbit.com/EN/Skin_diseases/Parasitic/furmite/fur_mite.htm
https://www.viovet.co.uk/Pharmaq_Ivermectin_Spot-On_Drops/c19097/
Xeno 450 is what vets often use. I visit a vet for mites, even after 25+ years of caring for hundreds of rabbits, because if a rabbit has mites, it's a sign their immune system is down in some way, and I want a vet to spot what else is going on for my bun
Good luck xx