I had a parasite that was deeply attached to me that I had to remove. I didn't use Damon Brands methods, so I cannot speak to them.
If you are sure a parasite is attached (that's on you to determine) you should find out what this parasite feeds on (you probably already know). Is it fear, lust, anger, rage, etc?
Once you know this, you can watch for those types of thoughts and behaviors, and change your thoughts consciously in those moments. Starve it out by not feeding it. Tell "I will not feed you!". I mean say it out loud as many times a day as you need to. Feeding it means giving into those thoughts (anger, lust, fear, etc). It wants/needs you to think and feel those things so it can feed on them. Thats all it does.
This is less about a ritual (a ritual isn't going to completely absolve you here, though it may help) you have to do some work in the mundane with it or it can just come back later, or pretend it left for a while. It is going to do everything they can to survive and feed on you. So if your habits and behaviors dont change, if it doesn't come back, a new one just might attach itself. This is much more common that people think.
It took me about 2 months to fully starve it out. It was fine at first, but after a while it got tougher. It was fighting to stay, fighting to feed. Some of the thoughts weren't mine. Obsessive thoughts that weren't my thoughts. I had to fight them and starve the fucker out. Over time, it got easier, it was still there but wasn't as strong. The thoughts lessened. Finally it just detached completely. Yeah fuck parasites, they are no joke.
Bonus: My ritual success exploded after the parasite was removed. I had way more energy to use for magick and ritual. Again, something most dont consciously think about. Hopefully you will see a marked boost in your energy for magick and rituals as well.
This is just my personal experience with it, and by no means the only way to deal with a parasitic attachment. Take what resonates and burn the rest.
Good luck!!