I agree that you should make it with the same ratios as you usually do—do everything the same, including the time spent boiling and the amount that you reduce it. That way you know exactly what you're giving your friends. If you aren't usually very precise, I'd do a run of your usual one dose recipe with a timer, some measuring cups, and a pen and paper so that you can make it precise and repeatable and then scale it up.
If you didn't already have a method, here is what I've done successfully. I'll scale it up for 8 doses for you. Each final dose will be about 1/4C liquid. Even if you don't use this exact method, maybe it will give you some technique ideas.
1) Grab the pot you'll use and pour in 2C of water. Find some way of marking the height of this amount of liquid in this pot. For example, maybe make a mark on a popsicle stick. Later, when you're reducing the tea, you can use this to know when you're done. Discard the water.
2) Put this in the pot:
- 16C hot water
- 24g rue seeds
- juice of 1 lemon, strained (any pulp grossifies the final texture)
- shake of ginger powder for nausea
- very small pinch of salt for taste (such as it is, lol)
3) Boil hard (very high heat) for ~30 minutes, keeping an eye on it to make sure it doesn't boil dry. Use the popsicle stick (or whatever you're using) to know when you're done.
4) Pour the mixture through a strainer into a collection vessel.
5) Optionally, for a little more efficiency, add a small amount of water (1 or 2 tablespoons) to the pot. Swirl it around to get all the good stuff left behind, then pour this through the strained seeds into your collection vessel.
6) Divide evenly between eight cups.
I had a wonderful experience last night with this method!! Vaporhuasca is just pure fun.
This mixture may end up being stronger than the one you usually make, but I can't say for sure based on the details you've given. There are ways to make it more resource-efficient, but I like that this way doesn't take very long, and, even though I've divided it into micro-steps here, if you think about it, there's really only one step lol. Plus the cleanup is easy.
Finally, I'll share a tip I was delighted to discover recently, which is that the perfect chaser is a fatty liquid such as whole milk, creamy oat milk, or even coffee creamer. If you plug your nose while drinking the tea and the swish and swallow the chaser without unplugging it, you never even taste the rue.
Quick edit: I realize that I write kind of like an llm lol. I like em dashes and I like formatting. I promise I am a person!!!!