They have pass over before they see any light. My Goddess Morrigan will escort them to the other side if you ask nicely. She will not on the other hand do all the work for you. If a rite is not done right in getting rid of spirits you can make it worse not better. You must remember this your world not theirs and never show fear.
Energy can feed the problem.
This why Spirits prefer children over adult to make contact. I myself do channel and spirit card work. I call upon them while I read the tarot cards. Anyone can do so if you learn to channel. That is much as I can tell you on that subject.