Some claim blend, others thermolysis, and others galvanic. For coarse or medium fine facial hair what is the best treatment that would cause less irritation to the skin and would guarantee the highest kill rate, meaning that once a hair is zapped, it’s gone for good? I’d love to hear what various electrologists have to say about this. I have started on blend, but some say (including my electrologist) that thermolysis can be just as effective. Perhaps I should use my face as an experimental canvas 
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Your electrologist is right. Any modality can work on your hair, the best modality to use depends on the hair, equipment used and the skill of the electrologist in a given modality. If she is highly skilled in thermolysis and has good equipment, than there is no reason it cannot be as effective as galvanic or blend.
You may want to read electrolysis section of this forum where this is often discussed. Any of those modalities are great in good hands. Thermolysis is fastest however.