Some people first give the shrub a hard spray of water, idranoel. Their weak bodies cannot stand this and many are killed. Repeat agin to make sure that you also kill newly hatched mites as well.

If the infestation continues then mitices are recommended. These have to be reapplied two or three more times about 7 days apart to kill the mites from eggs that hatch.

Sounds more like tea scale than mites. I have a similar, pernicious problem, and I spray neem oil alternated with sunspray oil (be sure to cover all leaf surfaces, top and bottom) several days apart in an attempt to keep them at bay. It's not an easy problem to solve, and I've read of people who cut their shrubs all the way down to rejuvenate them and eliminate the pest. I'm not brave enough to try that, yet!

Sounds like tea scale to me, as well. It is the males that coat themselves in a thin, white coating....which they will vacate during their last molt. Horticultural oils are typically recommended for this scale. Just read and follow the directions on your product carefully for mixing rates and the timing for repeat applications.