Flare, extractions range from semi-complicated chemistry processes to something equivalent to making a pot of coffee. 
Alcohol extractions are slightly more complex than making tea or coffee (which is also both a live extraction!).
If you have whole cactus you need to do this step anyway: chop the cactus into pieces after removing the spines and use a mixer/blender to grind it to bits. Powder if its dry or mush if its fresh.
If it's dry powder you have, add a small bit of water to it because I believe the extraction will work better with some in there.
Then add an alcohol, preferably not denatured since that contains a little nasty stuff, I use isopropanol (= isopropyl alcohol, IPA or rubbing alcohol) - sorry but look elsewhere for the volumes...
Isopropanol should be equally or less expensive than high proof ethyl alcohol / ethanol.
It is only slightly more toxic than drinking alcohol but remember drinking alcohol is really a poison. Getting either of them on your hands feels a bit cold from the evaporation but it's not harmful. Don't go drinking it and you'll be fine!
Then after steeping for a certain amount of time like tea you have to strain it by just pouring it into a coffee filter. Then collect the liquid and throw the solids into another volume of water + alcohol. This will be the second "pull". Do 3 pulls and pool all the liquid.
You might want to let this liquid stand so that tiny particles stick together in the course of hourse or days (I think even better in the fridge) after which you can filter it again for purity.
When this is all done you need to evaporate all the liquid. What is left is impure mescaline that is much easier to ingest than the whole cactus. In my opinion it is worth it, personally I'd say if you don't want to do this don't bother at all because unextracted cactus is too vile a task to eat/drink.
The evaporation will take a lot of time to do spontaneously, if you set it in the baking sun it will definitely go faster but if you can get a hotplate or gourmet plate or whatever that gets hot without the flame you can set a PYREX baking dish on it with the liquid in it to boil.
Using a pan on a hot stove is dangerous because the alcohol vapor is a little flamable. It could be done but only if done very well and careful! Be warned.
What you're left with can be scraped up and eaten.
And lest we forget: trip on! :D

Alcohol extractions are slightly more complex than making tea or coffee (which is also both a live extraction!).
If you have whole cactus you need to do this step anyway: chop the cactus into pieces after removing the spines and use a mixer/blender to grind it to bits. Powder if its dry or mush if its fresh.
If it's dry powder you have, add a small bit of water to it because I believe the extraction will work better with some in there.
Then add an alcohol, preferably not denatured since that contains a little nasty stuff, I use isopropanol (= isopropyl alcohol, IPA or rubbing alcohol) - sorry but look elsewhere for the volumes...
Isopropanol should be equally or less expensive than high proof ethyl alcohol / ethanol.
It is only slightly more toxic than drinking alcohol but remember drinking alcohol is really a poison. Getting either of them on your hands feels a bit cold from the evaporation but it's not harmful. Don't go drinking it and you'll be fine!
Then after steeping for a certain amount of time like tea you have to strain it by just pouring it into a coffee filter. Then collect the liquid and throw the solids into another volume of water + alcohol. This will be the second "pull". Do 3 pulls and pool all the liquid.
You might want to let this liquid stand so that tiny particles stick together in the course of hourse or days (I think even better in the fridge) after which you can filter it again for purity.
When this is all done you need to evaporate all the liquid. What is left is impure mescaline that is much easier to ingest than the whole cactus. In my opinion it is worth it, personally I'd say if you don't want to do this don't bother at all because unextracted cactus is too vile a task to eat/drink.
The evaporation will take a lot of time to do spontaneously, if you set it in the baking sun it will definitely go faster but if you can get a hotplate or gourmet plate or whatever that gets hot without the flame you can set a PYREX baking dish on it with the liquid in it to boil.
Using a pan on a hot stove is dangerous because the alcohol vapor is a little flamable. It could be done but only if done very well and careful! Be warned.
What you're left with can be scraped up and eaten.
And lest we forget: trip on! :D