Method described by chronic is essentially what I have been doing.
With salvia, I like to remove 1 or 2 node sets that will go under the soil line. I do not remove or cut in half any of the leaves as I would with many other plants. Salvia seems to do better with the leaves intact even though I often lose the lowest leaves during the process. I plant the cutting into a soilless mix (coco or promix) in a 1 pint or 4" pot. I sit the whole pot and cutting in a 10x20 seed tray with 7" humidity dome, vents lightly cracked. I can fit 3-5 cuttings in each tray and dome. Twice a day I remove the dome for 5 mins and spray the inside of the dome with water. If plants looks parched I spray the foliage too. After a few weeks roots are coming from the drain holes and I begin to harden them off to outside the dome.
For M Speciousa I have good success with the same method listed above (except I half the lower and mid level leaves) when it is just 2 or 3 cuts I have taken. When I want to take 25+ cuts I like to use 1.5" oasis cubes. Same process for most part though. Open dome two times per day and spray dome inside. One thing I notice.. M Speciousa likes to stay very wet \ humid for the first 3-5 days. If you don't they can start wilting. After 3-5 days you wanna back way off on humidity though or they will start rotting. They seem to need time to ease into rootless life without wilting heavily.
Hopefully something in there helps. Ill add pics.