There are hundreds of pagan religions all of which believe different things. Hindus have a different world view from Taoists yet both are pagan. If a particular pagan religion believes in demons then it will have a ritual for casting them out. If they don't believe in demons, they will have no such ritual. You would need to look at each religion separately.
No power. Only ignorant people who want to believe the nonsense they've been spoonfed their whole lives believe Pagans use demons, only because the deities Pagans worship are considered demons by one religion or another.
And for the record, I don't believe in demons either.
Pagans don't cast out demons. How do you cast out something you don't even believe exists? I have known pagan priests to help get rid of dark spirits, but that is not the same as 'demons' or 'devils' in the Christian sense.
I think the demons are a culturally understood explanation of mental illnesses and frightening diseases such as epilepsy. Jesus cast out demons more or less the same way He healed diseases. Demons are something of an anomaly in the bible. There's no real explanation for them, and they just kind of appear in the text more or less from nowhere. It could be cultural contamination from African religions to the south.