Citric acid spray (lost coast plant therapy) works VERY well. Key is to spray UPWARDS, as most of the mites live on the bottom of the leaves. If you have webbing on the buds also spray top down. I did it every day when the lights come on, as this gives the dehumidifier more time to work.
I did it every day for 3-5 days. Then back down to every 3-4days. I am helping a friend with them, and we have them heavily mitigated. Once the plants are done we will purge the room with heavy duty pesticides.
This worked for me, predatory mites did work too but not as well.