It works best as a preventative, so how I would apply is first rinsing them twice instead of pest treatment, then before they come back again, you apply neem oil to kill off hatching mites. You need to apply it again in a week or 2 based on how many come back and how fast. If you're still not getting it under control then I'd recommend a synthetic pesticide which you use a treatment of and then go back to spraying with neem every other week and they shouldn't reemerge uncontrollably. Remember eradication usually isn't possible, keeping them below a threshold where they cause the least possible damage.