Yes, tea, not the entire cactus. Har har.
TL;DR: It barely worked. Extremely minor threshold effects. My guess is my specimen had very little mescaline content or I lost it during the extraction process. However, the actual plugging involved no pain or discomfort. I plan on attempting it again.
Long version: Prepared a standard tea of 3" diameter, 1' length non-PC SP through two boiling sessions with some lemon juice and DI water. Strained the pulp through cheesecloth til it no longer tasted bitter. I allowed the tea to sit in my fridge and separate into layers (a dark green slime formed on the bottom of the container; I separated this from the top layer of lighter green liquid through slow pouring. I tentatively suspect that this is where I lost most of my alkaloids. I believe that the denser, alkaloid-rich liquid was nearest to the slime, which I did not bother drawing out as I naively assumed the rest of the liquid would be rich in alkaloids).
I reduced the volume of liquid to about 50 mL and drew it into a turkey baster (I had to do this twice since the turkey baster only held 30 mL). I coated the turkey baster in coconut oil and inserted it into my rectum about 2.5". I then raised my butt into the air and squeezed the bulb; the liquid gently poured inside, there was no discomfort (I was worried about the acidity of the tea causing burning) besides the turkey baster shoved up my ass. I clenched tightly and held it for a few moments, after which time I was able stand and move about without any leaking.
After 10 minutes, I experienced the urge to evacuate my bowels, but it quickly subsided. After 40 minutes the urge returned and with a vengeance and I had no choice but to evacuate my bowels. The excrement was oily and liquidy but not green at all. I was confident that I had absorbed the majority of the alkaloids at this time because of the high bioavailability of rectal tissue. People have tripped off of mescaline after purging 40 minutes after ingestion, anyway.
At T+1:00, I decided to smoke some weed. After smoking I noticed very minor OEVs (so slight that it could have been placebo). I felt slightly higher than usual even though I smoked a relatively small amount and suspect that it was at least partially potentiated by the mescaline, though once again this could have been placebo. All in all, effects were scarcely noticeable -- I attribute this to the cactus and my extraction rather than my method of application.
The next day my excrement included a small amount of white stringy-slimy material which I suspect were fibers from the tea that remained in my bowel after the application.
I don't write this to be mocked, I write this for anyone who is interested in attempting the method. Yes, I could've drank the extract, but frankly I would rather shove a turkey baster up my ass than taste the leafy battery acid that is San Pedro ever again. I also could've done a crystalline extraction. I chose not to, for a variety of reasons.
I will be attempting this again in the future, hopefully with better results.
EDIT: For future cactus pluggers, here is an updated post in which it actually worked (with a Bridgesii):
https://www.reddit.com/r/mescaline/comments/921u6c/so_i_plugged_bridgesii_tea_up_my_ass_again_with/