From the outset, I'll give this precautionary warning: don't take a demon onto /into yourself. While they might try to delude you and give you the impression that it's necessary for the protection of others you feel they might be apt to harm (taking advantage of that oversized Heart of yours), it isn't. Period. You'll be long past running down the street naked (or variations thereof) before you remember what it is you'd agreed to.
(And make sure you have 'permission' before you exorcise or remove anything. As much as there's no such thing as a 'mistake' in the grand scheme of things, you wouldn't want to remove an entity that's present as part of the Divine plan of someone's ascension. If you're unclear about that, please contact me.)
I've heard a lot of mentions lately about what colour /variety of Light you should surround yourself with, but sometimes, in order to see something that's particularly hidden, it's immensely helpful to visualise yourself in Black Light. Actually, visualising yourself 'as' Black Light would be more to the point. As an immortal Being /soul, you've got Nothing to fear doing this (and if you think you do, it's a mind-job, and it isn't doing you any favours). If you prefer, think of it as though you're using glasses with coloured lenses, except in this case they're not rose- but shadow-coloured!
At this point, you can just let whatever's under the glass spin itself out. It'll start refracting and dispersing, transforming into (something else). Don't worry that you might be 'hurting' it in some way; in effect, you could say that you're doing it a favour. Actually, all you've done is put it in a position where it can be readily observed. The rest of what happens it's doing on its own.
Stuck on something? If you're not aware of me having visited you with an answer already (Hahahahaha), there's email: email@example.com It's a little slower, but it gets the job done (and in Divine timing, too!).
Otherwise, there's this option: 'Behind the Veil'
Big Medicine Love to You