You didn't say if you lived with your master. As far as you learning what to expect with enemas, I STRONGLY suggest that before you start playing with your master, that you, on your own, just go to a drug store and get a cheap enema bag and have several enemas on your own while he is at work. This should be easy to accomplish if you live alone, and NOT too hard if you live with him. Learn how YOU feel with various volumes of enema solution, held for different periods of time.
I can't help it, but the way you wrote, I get slightly bad vibes and hope you don't get hurt or taken advantage of in the early stages of your enema play. When I was younger and in high school and college, I was very dominant to my boyfriends, sometimes brutally so, including the one I met in eighth grade that I eventually married when we finished graduate school. (I did a lot of things to the boys I knew that those macho guys would not have wanted to be known, such as tying them up, and dildo butt fucking them and the like, before I allowed them to have sex with me. That enabled me to practice some S&M in high school, get oralled a lot and NOT get the reputation of a girl who had a lot of sex.) Anyway, the first time I gave my boyfriend, now husband an enema was Friday night after finals week in college when he forgot we had a dinner date. He came over three hours late, and thought he was going to spend the night. I told him he couldn't sleep with me unless I gave him an enema. This was a surprise to him and he had never had an enema before. I smacked his butt a number of times, but I slowly and lovingly gave him one quart of plain warm water and played with his balls while he filled up. I wanted him turned on and wanting to to this again, not grossed out, in pain or having cramps. I hope you can work out something with your master that gives you an equally rewarding first several experiences. After you become accustomed to your enemas, you can work in pain and punishment.