I am currently working as a scribe, this is my gap year between college and med school.
It is fantastic clinical experience. I worked as a CNA a few years ago and this is so much better. As a CNA, I was interacting mostly with nurses. As a scribe, I interact with doctors - all day. Yes, you work with doctors all day every day. With my company, we work with a doctor the entire shift - wherever they go, I go! I'm in the ED and I like it for the most part because you get to see a huge variety of cases at different acuity levels. Scribing is also fun because you start to learn a little bit of medical decision-making.
It didn't help me much for my application because I started working after I submitted my AMCAS, but I did send update letters about my experience. I was also able to talk about it interviews, which was probably the best part of this job. My interviewers were so interested in it and wanted to know more about it. One of them even said, "I think every doctor should have a scribe!" I was able to talk about how I currently work in healthcare, I know how it works, I know the downfalls, and yet I still want to be a physician. It also made me see how different parts of the medical team (doctors, nurses, PAs, techs, scribes, etc) work together, and interviewers really liked to hear how I know about the collaborative aspect of healthcare.
Since I haven't started med school yet, I don't know how much it will help. My suspicion is consistent with what you said, it will help for 3rd year rotations as we literally write medical notes all day. I also think it is helpful to be learning the "language" of medicine.
My company does not allow patient contact, which is just fine with me. I did enough vital signs, cleaning patients, etc when I worked as a CNA. I actually prefer this because I truly get to observe the physician while I'm there. We definitely are not allowed to do procedures!
The employment process depends on the company. I work for one of the larger scribe companies that the hospital has a contract with. I have heard it is better if you can get a job where you're directly employed by the hospital/office, as you usually get paid more. I applied for the job, was contacted within a few weeks for the interview. I was supposed to have an in-person interview but something came up so I ended up having a phone interview. It was a general job interview, nothing too crazy. It probably lasted 20 minutes. Heard back that I got the position that evening. I started training maybe 3-4 weeks later. We had 12 hours of classroom learning (4 days and 3 hours each) where we learned some terminology, basic physiology, how to write a History & Physical Exam, and we had a few tests/quizzes. All of these were provided by the scribe company. Then we had 5 shifts (40 hours) of training on the job. If you were not fully competent on your own during that 5th shift, you were fired. I don't believe prior medical experience is needed. I did have some but most of my colleagues did not. You need to demonstrate a sincere interest in the medical field. Everyone I work with is pre-med or pre-PA.
The need for scribes is highly dependent on the area, from what I've been told. My group is always hiring, but I know there are some cities where it is harder to get a position. It's a job with a quick turnover rate. Most people are only there 1-2 years (some even less) as we are going to professional school after scribing. The worst part of the job for me is the pay. The schedule is also something that is difficult for me. Since the ED never closes, you work whenever. Days, evenings, overnights, weekends, holidays. I'm glad I'm doing it on my year off, as I think it would have been difficult to manage during college. Some scribes work in offices that are open 9-5, that may be an easier place to work as far as scheduling. I like the variety of cases in the ED though.
Oh and as far as drug tests, there may have been one for the hospital where I was hired. I don't think the company required one, but the hospital may have. They don't do random drug tests where I work, but honestly this is probably location-dependent.
Feel free to PM me if you want to know which company I work for. Good luck!