Here is a thread where we have been discussing shots ad naseum lately. Also, in the second post of that thread, James C. linked his injections thread - very much worth reading.
Welcome to HW. You don't say if you are a prostate cancer patient/survivor, and that may make a big difference in how your insurance company treats the meds. I don't know exactly what mine covers (not much except for PCa patients), but they did allow (I pay, goes against the deductible) 10 ml per month (Trimix), and the Rx is to use 0.2 ml per shot (I only need .13, but there has to be a dosage for the law). I expect what the doc writes on the Rx will have nothing to do with what you actually use. If he writes 0.5 per shot, and you need 0.1, you'll be ahead of the game. Discuss that with him. Maybe he knows the company's scheme.
You mention several trips to the doc - at least for Trimix, the Rx was called into my compounding pharmacy, I picked it up, and made an appointment. I did the first experiment in his office as training, with the real stuff. Once we came to the conclusion that it worked, he gave me a plan on how much to increase the dose in steps, and instructions on what local ER would be the best prepared to deal with that feared 4-hour woodie, should it happen. Each time I am thinking about adjusting the dose, I consult with him first. I will say it is all new for me as well, and I and adhering to the rules to the extreme.
Some docs do dry runs without the actual med to train, and I've heard of others that dispense it themselves.