For frotting fuckerella's sake don't eat raw cactus ... it's usually the prelude to a long and nightmarish vomitfest.
Here's my grandma's old recipe, dating from sometime around the Abdication Crisis:-
1. Grind the shit into powder using a "coffee" grinder.
2. Boil the powder in copious, acidified water for half an hour.
3. Filter the resulting snot through an old t-shirt (much squeezing, wringing and cursing required.)
4. Boil the filtrate down to a quaffable volume (half a cup is good.)
5. Add lemon juice to taste.
6. Take a wide-bore drinking straw. Jam it as far down your throat as you can without gagging. Use it to suck down the snot, trying to avoid all contact with the taste buds.
7. Dose gradually - take half an hour per 25g of cactus.
This should result in a pleasant, vomit-free experience with a comfortable come-up. It had better, because you'll be under the influence a long time ...