I've been able to get rid of spidermites with mighty wash.
One thing I learned when I was working pest control, a lot of defeating pests is understanding their life cycle. Spidermite eggs hatch 3 days after being laid.
3 good sprays with mighty wash can do the job.
I use a pump spray. Spray the shit out of the plant, top of leaves, bottom of leaves and stems. 1 week later, same thing, and 1 more time a week later. Ta-da! Mites gone.
Now this is in veg only. I have had mites once in flower. I came back from vacation, a few days from harvest and didn't make an attempt to rid them.
Oh, indoor cure.. outdoor? Little harder to fight. I'm probably no help there. Rotating products is not a bad idea either... if you're constantly battling that is
SH420