I recently forced a patina on a bit of my brass EDC kit, and the end results were fantastic.
To achieve this patina: Add roughly a 1/2 cup hot vinegar to a mason jar, and mix in a teaspoon of salt. The more salt, the more aggressive the patina and speed. I used a teaspoon, and had this look in about 10 minutes. Tie string to your brass items, and suspend the item above the chemicals while using the mason jar lid to secure the string to prevent the item from touching the liquid. The fumes will be most potent up top, so if it is a long brass item like a pen, you may need to flip it after half the time, to get an even patina. Another approach is to use a wide shallow tupperware, so the long brass item can hang horizontally instead of vertically. I had my mason jar sitting on top of an oil heater to keep the vinegar warm and act as a diffuser. I sat and watched the patina develop over a few minutes, until I was happy with the results and removed the items. If turquoise buildup beings to form, you can buff it with a towel to knock it off but it will still leave a blue mark on the brass.