Are you talking the waxy outer skin, or the green layer just under the skin? There's a huge difference, there.
I am not sure about the solubility of mescaline in alcohol (it probably is), but I do know it is soluble in water. You could do a water extract, making a tea. Then evaporate the tea down to a resin. This has worked well for me.
You could boil for an hour, remove water, boil again for a couple hours, remove water then boil again for 4 hours (or until the pulp is no longer bitter to the taste). Then filter the best you can, reduce all of your collected tea on the stove to a small amount of fluid, and air dry with a fan/dehydrator/oven set on low.
Mescaline is not very soluble in acetone, so this would not be a good candidate.
Be an adult only when necessary.