How do you know if the clinic/technician is good or bad at doing SMP? What questions should I ask to evaluate them?

I want to do SMP, I have a couple of clinics I want to visit and get a consultation first, but I do not know much about SMP. So, I'm worried about who I should choose to do my SMP. My biggest fear is my SMP will look unnatural or wired and it will change to green or blue. so upon what criteria and qualification how should I choose my technician to avoid the above mentioned concerns. what questions should I ask them to know if they are experienced and good technician? p.s: I want to increase density.