I think you should go over to DMT-nexus. they have some very knowledgable threads and teks in the forum. The best tek always depends on the time /effort /etc. you are willing to put in... so best you look around and see what suits you. Its not realy rocket science, and you are familiar with some basic organic chemistry allready now. As I said look for something useing HCl... I think its about 6 drops of HCL per 100ml of water, but then I'm mighty stoned. Best yields is eating them raw.
Most of the teks are pretty straight forward requiring a solvent like xylene to seperate the mescaline into and then an acid to salt the mescaline out of suspension. + allternatively a few washes.
Ingredients are cheap and easily come by, like xylene from hardware store, white vinigar or even better vinigar essence, some active cacti and some water some pool acid.
I think Ron69's dlimo tek is pretty cool, but a friend had some issues with it being a bit tricky if I remember correctly, I'll ask him when I catch him online in chat over the weekend.