Number 1) a clone or cutting has no roots, as such the only thing you can do is feed the plant through its leaves, assuming your not hydroponically cloneing, and at that the only thing a clone really needs is water, whether it be by misting water on the leaves or hydroponically rooting the plant.
Number 2) the idea behind cutting leaves in half is to slow the rate moisture evaporates from the plant, however the method by which you slow the loss of moisture can be done quite a few ways, for example, by covering the plant with a dome of some sort, termed "humidome," due to its ability to keep moisture in the plants environment thus slowing the rate moisture can evaporate from the leaves and in fact encouraging the plant to draw in more moisture (of course fresh air is still key, so removing the humidome to have an exchange of air is necessary, followed by a light misting of the plants and humidome to replace the humid air lost)(the cheap mans humidome is a piece of plastic wrap draped over the plants fyi), then theirs just manually misting the plants a few times a day as necessary until they root. Theirs also a ton of different ways to hydroponically root clones which is to in depth for me to really cover now, but you can find through a simple search.
Number 3) Different plants react in different ways to rooting hormones, some really like them and root faster, while others react adversely. I personally have found it to be less stressful to simply root the clones without rooting hormones, which makes sense seeing as how that's how it happens most often in nature.
Number 4) And Iv'e already touched on this, the most important factor is water, its all that's really necessary until the plant has roots. And in terms of ease of use, cost, and success rate, i find jiffy cubes/root riot cubes/packed peralite or vermiculite to all work well while being very easy to set up and use.
i've never had a clone not root
