---I use small plastic containers with clear plastic covers. They are sold for food storage, usually left-overs. I sometimes just place the Mexican Pinguicula leaves on top of the lid of one of these containers and wait. It gets good light, but only the moisture from the humidity in the air. The leaves start to dry up, but, so far, I have most usually obtained a crop of small plantlets by the time the parent leaves have shriveled up to a husk. I then plant them. I admit though that I rarely do this. Usually I put the severed leaves into a ziploc with a small quantity of barely moist LFS instead. This produces larger plantlets and the parent leaves usually persist to continue nourishing the forming plantlets.
From my experience it is kinda difficult to not obtain new plants from severed Mexican Pinguicula leaves. About the only way this will rarely work is if you don't remove the leaves manually. Even this will not prevent it from eventually happening. Nearly all of them if grown successfully for a sufficient period of time will generate some plantlets from the bases of their old dying leaves, which will then crawl out from under the parent plant.
---I had used cinnamon oil, about 1 drop in 1 pint of water and sprayed it on CP leaves affected by mites. I had some leaf damage, I believe from the cinnamon oil. I now only put cinnamon oil on pieces of paper towel and place them on the back of my fans so it can volatize into the room. It is reported to have antifungal properties. I have never worried about fungus and I only use it to inhibit mites, which I believe it does.