How long from leaf removal to roots

[WayneByerly]

I've read that you can pull healthy leaves from a Echeveria, lay them aside to dry, and they will automatically start to sprout roots. I'm curious as to how long I should expect it to take from the time that I pull healthy leaves from the "mother" to the time that they start to grow roots? And yet once again, is a rooting enzyme recommended? And if so, WHEN should it be applied?

[esp_imaging]

A few weeks should be long enough. They will often start to sprout roots if just let on the soil surface, or windowsill or whatever, without being given any particular care, and without needing rooting hormone. Keeping them cold and damp is not recommended though.
Some species are much easier than others from leaves. E. lauii for example has a reputation for being hard to grow from leaf cuttings. Maybe hormone will help with the harder species, either at teh time of amputation or after a few days when the wound has dried.