Protection methods that work by calling on an external power can be very effective. The power you call on could be inanimate, such as the power of a mountain or the sun, or the power of a being such as a spiritual ally, an animal or an ancestor.
What’s important to remember is that you’re calling on something that’s currently more powerful than you, and hopefully more powerful than whatever you’re protecting against. This means that it’s got more energy available in it to make things happen: whatever you’re calling on should be pretty stinking big, energetically.
I’ve found in particular that a power many other people have called on can be very effective – ones I’ve used with good results are sacred mountains, Jesus and various angels. But you can also call on something very personal, for example if you know you have an ancestor who’s got the juice to deal with the situation, then they’re a great bet as well.
The most important thing to remember when calling on an external power is that they should intimidate you. They’re more powerful that you, right? You should feel that to your bones – and equally, you should have a good enough relationship with them that you know you can trust them to use that power well.
That’s why, while calling on another demon to get rid of a demon would possibly work, it’s not a safe solution in the long term. But that doesn’t mean you have to call on a power that’s ‘light’ – a neutral or ‘grey’ deity or ancestor could also be a good choice, and an example from my own heritage is Hella, Queen of the Underworld. Anyone who has ever called on her knows just how intimidating this kind of energy can be!