Love doing this to a woman.
Usually she is on her tummy and I pull her pants & panties down (or lift skirt). I put a hand on her lower back, firm but gentle, and spread her cheeks with my other hand’s fingers, just for a look at first. A long look.
Then I open the jar of Vaseline, open her bottom again, wide, and apply the lube to her anus. Just pushing the very tip of my finger in and twisting it a little.
Then I get the thermometer. Which I put in a glass of cold water first, so she really feels it. Again I use my fingers to pull apart her cheeks and anus and slowly insert the cold thermometer. Halfway. During the time it’s in her bottom, I check it, twirl it a bit, gently readjust it.
Once it’s over and removed I wipe her hole clean, sometimes asking the woman to hold her bottom open as I do.
Occasionally I take her temperature with her on her back with legs pulled up to her chest. Then I can watch her nervous or lusty face as I do the intimate procedure.