Did the proposed preparation entail heating? Might have described a process that destroyed most of the mescaline to spare you the experience, which can be quite frightening and/or debilitating.
I've never come across someone that does more preparation than drying, so to me it seems suspicious to suggest anything else. Mescaline is water soluble so one can make infusions, but it takes a fair bit of plant material to get dosed so there isn't much practical use in doing so.
No heating. I was just along for the ride, but I think it was something to do with removing hairs, and to make it less bitter.
Reducing bitterness likely reduces potency as well. Mescaline itself is quite bitter and whatever solvent is used to flush out other less tasty substances will likely solve mescaline as well.
Drying slightly improves the taste but not by much.
So me and some buddies got a hold of some peyote and were more than a little afraid of it. We probably would have tossed it but we had a better idea. We called Coach and asked his advice. He gave us detailed preparation instructions. We followed them and got a bit sick, but not altered. Maybe it wasn't even peyote.
I'm not sure that this approach was just more nuanced than "just say no" or closer to "just do it".