Some Phal species/hybrids are prone to produce more keikis.
I'm not sure how to make it with Phals but maybe increase nitrogen and keeping temps constantly warm.
Some theories say that it is a survival mechanism. If that's true, maybe putting it in a state of near death, which I don't think you want to.
I’ve played with keiki paste on flower spikes, but we have no control over what grows from the node, it all depends on what the plant cells have “chosen” to grow into. Once the cells have differentiated, the “will it be more flowers or a keiki” question has already been answered but we can only learn the answer once it grows out. It’s still fun.
I do have a phal. philippinensis growing two keikis, but this plant was a very strange situation. I’ve been meaning to update the thread I started about it.
I was also curious when I stumbled onto this forum. have been trying to see if it can be done without keiki paste and came upon these 2 videos and am presently trying out something similar to both of them. Will let u know in a couple of months if there’s any success!