I have a quick and easy way to prepare fresh cactus. I used about two feet of skinny bridgesii. I cut it up into one inch pieces and then froze them overnight in a glass tray. Next morning, I stuck them in the microwave for twelve minutes. I poured the juice from the bottom of the tray into a cup. Next I took the steaming hot pieces and used a handheld lemon squeezer to get the goods out. I squeezed each piece flat. I got about half a cup of juice and then poured it through a funnel with a cotton ball to collect small spines and snot.
To drink it, I first gargle some Pepsi, spit it out, and then chug the cactus juice. Then gargle again with Pepsi. The carbonation numbs the mouth and the Pepsi coats it with sugar. The cactus juice was painless.
I believe the freezing and microwaving breaks the cells and allows for maximum cactus juice to escape. You can save the flesh and do a ten minute pressure cook with minimal water if you want better extraction efficiency. I don't find it necessary though, the trips are strong. Best part is the ease and quickness. I don't puke this way either, like I do with purified HCL or acetate.