I am not super well versed in natural preventatives, as we have never really had to deal with mite/fleas in the past. However, in the last three years mites have been going crazy across my entire state thanks to record heat. You can use revolution for dogs, in the USA it is only prescription However you can buy it from this website and have it shipped over from Australia (buy the large dog one, it’s the exact same formula but a larger bottle for the same price). Just place two small drops on the skin behind the ears (you want it as far out of reach from them ingesting it as possible) and massage it in. and then you treat one every 30 days.
I had to treat my herd just last month, it was my first using the product, the results were practically instantaneous, the next day all of them were dead and I just needed to brush them out. So far it doesn’t seem to have any negative affects on the rabbits ether. It is the most common flea treatment for rabbits, both prescribed by vets and in the show/meat community.