I spray with a bleach solution, then immediately spray with water. Repeat a couple days. Then the spider mites go away for a couple months. Thanks to their small size, this is doable.
I don't mess with the bleach. I wash with my thumb on the hose end under the bush's once, maybe twice a week and never have and problems with spider mites. The HATE water.
Like Ken said, a hard spray with the hose under the leaves will wash them away and is much safer than fooling around with bleach.