Personally, I do not like the terms "ghost hunter" or "ghost buster" - simply because ghosts are people. Our society tends to view them as some strange, unwanted pest, and I feel that is disrespectful. "Spirit Rescue" is a much more preferable term, in my opinion. However, ghost hunters are typically out to prove the existence of ghosts, not rescue them.
So, what does that mean, "Spirit rescue?" It means helping the spirit to move on into the Light, and not be a "ghost" anymore. The added bonus, of course, is that the live people dealing with the ghost will be free of the fear and discomfort also. Part of me wants to say that anyone can be a Spirit Rescuer. But at the same time, I feel that is not true. I believe that a person who feels drawn to this type of work will have some mediumistic ability (Mediumship = communicating with Spirits). In order to fully help a spirit move on, there are several factors to consider.
Does the spirit want to move on? If not, why not? They may have issues they want to resolve first. They may be afraid of eternal damnation, and it is the Spirit Rescuer's job to convince the spirit that that will not happen. Basically, we need to alter that spirit's perception of God. Not an easy task if they are set in their ways! They may not even realize they are "dead", and will need this explained to them. Some may realize they are "dead", but not realize that they can move on, into the Light. They just don't see it as an option. Some may not see the Light, and it will need to be pointed out to them. Often the Spirit Rescuer can call in the spirit's family members or Angels/Guides to help the process along. It is not unusual for a Rescuer to need to work with a spirit over time, to help convince them that it would be in their best interests to move along. It's not usually an instantaneous thing.
What about calling in a Priest to do an exorcism? Well, sometimes it isn't that simple. In my opinion, exorcisms are usually effective on non-human (demonic) spirits. But not always, at that! Some of these spirits (human and non-human alike) can be incredibly stubborn. It doesn't usually play out like the movie, "Ghostbusters" -- we can't just pop them into a little box and store them away somewhere. Which brings me to . . .
What many people fail to realize is that these spirits DO have the right to stay exactly where they are. How would you feel if someone came along and told you you had to leave your home or wherever you happened to be? If you refused, they could pick you up and bodily remove you, but we cannot do that with spirits because they don't have bodies. These spirits can choose to stay exactly where they are, for as long as they desire, and there isn't a thing we can do about it. Now, having said that, if we are being terrorized by an entity, that begins to infringe on OUR free will, and we do not have to put up with that. There are a lot of spiritual protection measures we can perform to protect ourselves and our families. My strongest advice is: if you are being terrorized by a ghost/spirit in your home and you feel threatened by it, remove yourself from the situation. I know that isn't an easy thing to do, but really, when it comes right down to it, homes and material possessions can be replaced, people cannot. You and your family are much more important than anything else. I cannot stress that enough. Once you are safe, consult a qualified spiritual practitioner. They can still work on removing the spirit from your home, even if you are no longer residing there. This type of work can also be done at a distance, they don't have to physically be at your house, though it does often help.