I often check the bottoms of my D. binata and D. capensis pots for root protrusion.
And as more likely than not, I find a couple inches of roots growing out. I then gently snap off 1" to ½" sections and then plant them horizontally in separate pots of standard CP soil mix under about ¼" of loose soil.
I figure that the heat from the grow-lights (or sunlight outdoors) causes new growth to quickly burst forth (3-4 weeks) into the waiting environment. It's really quite amazing to behold...
I've never had luck with leaf pullings however. Fungus or rot always destroyed the leaves before any sprouts appeared.