Just put keiki paste in the search box and read the first couple of past threads that come up.
Unfortunately the search will also find all the numerous past threads on keikis (without the paste)

Define "expert". Lol.

Leave the keiki on until it has at least an inch of root, maybe more. There is no rush to remove it and doing it too soon will reduce the chances of survival.

It sounds as if you are talking about trying to induce a new plant from a branch in the main flower spike on a plant with just one crown.

As arthur says, you may find some advice in a thread on keiki paste. These describe a way of inducing a new plant on a spike.

However, there is no chance that potting a spike or branch of spike will give you a new plant.

There was a thread recently on a cut spike in water that produced a keiki. Also, I have seen keikis form on the stub of a cut spike, when two nodes were left on the cut spike. But this is not a sure thing. And you don't pot the spike, you wait for it to make a keiki.

"Keiki" is Hawaiian for "baby.' You can google keiki paste or find it at larger orchid nurseries on line. I think even Charlie's Greenhouse catalog has a keiki paste or clonal paste. At any rate, you apply the hormone past to one of the nodes on the stem. Wait till plantlet forms leaves and roots to remove and pot up.

If you already have a plantlet on the spike, you might consider wrapping some barely damp sphagnum moss around it's base and any roots it might have and then covering that with plastic. Check the whole package once in a while to see if roots are forming. Once a good root system forms, the plantlet can be potted up as a separate plant.

If you have any liquid seaweed you might consider soaking the moss in a weak solution of perhaps a teaspoon to a quart since seaweed encourages roots.