I dont know that many of the DIY'ers post here a lot regularly, I'm probably the best known here so I'll try and answer your question.For reasons that will become obvious, I'm not sure it's politically correct to relate this here, but well to hell with it.
As to pain tolerance, first I feel this does vary greatly from person to person, based on their experience to pain, what drugs they may be on to control pain, what they have eaten or drank recently, and a number of other factors.I'll try to draw on some of that experience to at least partially answer your question.Not all of this experience or knowledge comes from doing electrology however, some of it comes from some rather ahem, unique experiences I'm not fully comfortable talking about in an open forum, but knowing them gives perspective to the answers so I will anyway.
Long before I inserted my first probe into skin, I had experienced pain, as a pleasurable experience. That doesnt really sound right, but it's known that I have in the past been involved kink, specifically as a bottom to a particularly skilled sadist. There is a mindset or concept amoung people who live that type of lifestyle of "good pain" and "bad pain" that is, pain one wishes to experience and pain one does not. The trick part is that someone who has had extensive experience in feeling pain as an experience, begin to develop the ability to turn "bad pain" into "good pain". So that much is related to the persons "experience with pain". No matter what the source, if someone has experienced pain with any regularity throughout their lifetimes, they often have the skill to perform this mental trick. It doesnt have to be in that form either, there can be many sources for such a skill, say a disability or injury for example. In some cases disabled people can do it. So Mindset, and the ability or experience pain as not necessarily a bad thing, comes into play rather highly.
And for anyone wondering, no it's not a part of my world anymore and hasnt been for a long time, but the skill of turning the pain into a posative experience, will last a person a lifetime.
Another thing that experience taught me many years ago, is that physical condition, can mean the same pain felt with the same intensity, can be felt differently based on the persons physical condition. We know that things like caffeine consumption, sleep deprivation, stress, and a myriad of other factors, can vastly change how pain is perceived. The worst experince pain wise,I have ever had with a client was when they came to me after staying up all might and day after a overnight double shift.
Finally, there is a physical response to pain.This is often experienced by long distance runners, when they talk about "getting their second wind" . Your body reacts to pain that is experienced repetitively by producing a compound called endorphins. These endorphins reduce the pain sensations and produce a euphoric experience in mind and body. Chemically, these endorphins are identical to cocaine. IT is a very strong naturally occurring pain management system that everyone has to a certain extent .
I will say, that when I began electrolysis, I did use that mental trick, as well as a tolerance built up, to make the experience more tolerable. Perhaps that is why I had mostly completed my face, before I ever used any topical anaesthetic like lidocaine. I use it now for my neck, but I dont HAVE TO. Doing electrolysis to oneself, and seeing the progress, can be a very powerful motivator to mentally turn the pain experienced into a positive experience. I think however the most headway can be made by making sure one has enough sleep, is adequately hydrated, limit caffeine intake and has reduced stress. Once all those are in place, it becomes much easier to turn the pain into a good pain. You mind, and body, are better prepared for it.
I havent done a double session, though I might soon because a client has apparently been inquiring about it. There is not any advantage to it, not from pain management side, nor financially because you are then paying two electrologists. However there can be a physical disadvantage to doing so, in that if both electrologists are working on say the face, the head can only be positioned in one way, and this can be a good position for one, but less than ideal ergonomics for the second.
For your third question about scar treatment, I'm going to refer you to Mr Bono as I feel he has more experience than I in the medical side of scar treatment. You may however want to review his older video on telangitron located on his youtube channel here:https://www.youtube.com/watch?v=29_cqo1v1vI
this video partially addresses scar treatment with thermolysis, and may answer part of your question.
By the way, your site is looking good! I wish I was better at web design, I'm beginning to see the need for before, after, and much after pictures of treatment site to show what normal skin reactions should look like. I was talking to my partner today, and since we will be doing some practise work on each other in upcoming weeks, we are considering taking lots of pictures as we go along for this purpose. I encourage you to do the same. Because of copyright issues and client privacy, it's not always okay to use photos of clients, and one thing I've realized is that I didnt take enough pictures at various stages of treatment of my own treatment. Please, take frequent pictures even if you dont think they will be useful, they will be in future.