At some point during your training, Dom de Luxury may employ a device she calls the "Mind Control Ring". This is a highly effective training tool. I can tell you from personal experience that while it is hard to keep anything clear in your mind when you are with her, once she starts using this device on you, it becomes completely impossible.
These devices are relatively inexpensive. The problem with them is that they can be used only once or twice before the battery runs out. Once that has happened, there is no easy way to replace the battery, and you have to buy a new one. This is money that would be much better spent on makeup, clothes, shoes or more sessions with Dom de Luxury. Replacing them a few times a month or a week adds up to quite a lot.
If you look around, you may find some articles on the web which explain how to replace the battery. This involves disassembling the vibrator and is tricky and error-prone. There is a much better way. And not only is it cheaper, but it delivers a much more intense experience.
The two big names here are Durex and Trojan. The Trojan ring is slightly more expensive but much easier to modify. Purchase a Trojan mind control ring from your local drug store (probably cheapest) or from here. Then purchase a 'vibrating bullet'. You can get them from here or from a local shop. This is a decent price and they are well made. You will also want to get a pack of batteries. I bought these from Amazon, and I think they are a great buy. They last a long time and are very inexpensive.
The rest is very simple. Use the Trojan ring until the device it came with runs out of juice. Then remove it gently and throw it away. Put a battery in the bullet, and slide the bullet into the place formerly occupied by the Trojan device. That's it.
Occasionally, the bullet may not start vibrating. In my experience, this is always because the cap is not tightened enough, or is on slightly crooked. And of course, you will occasionally have to replace the Trojan "ring". Once or twice a year, at most, in my experience.
I hope this will be helpful in your training. If you have comments, or have found a better way, you can message me on Twitter