Well, I'll tell you...you're a new believer, but you're eager to learn, asking us, and that's good. I would say mostly, God can do it quickly, in one shot, however, we read that the apostles couldn't cast out a certain demon, and asked Jesus why, and He said, this kind only comes out by prayer and fasting.So in certain cases, there might be specific circumstances.Also, when you say, "a one and done deal", the demons could be cast out in one shot , BUT if at some time in the future you "backslide"{go back to a previous sin, that opens the door to demons comning back,like an invitation, like an occult practice, that might bring them back. So they could be expelled in one shot,but it's an ongoing process keeping them out.