When you get to talking about the number of parameters in taking cuttings, then the preparation of the cuttings, then the rooting method, it does seem a little complicated.
When you get some personal experience, its really very easy, and when you find the things that work for you then its a very quick procedure.
I'd do the reverse of what youve just done.
If a cutting has very soft growth at the tip (but only if very soft), then I'd remove it (razor blade, just above another set of leaves)
Id then remove the very lowest leaves - razor blade on a piece of wood.
If the remaining leaves were big, I'd cut them in half.
I need at least one set of side leaves on the cutting.
My thinking is that new growth, i.e. when the cutting starts producing new growth (a sure sign of action at the roots) the new growth comes from the axils - where the side shoots, or leaves, meet the main body of the cutting.
Thus I'm preparing with those side shoots mid way on the cutting in mind - for producing new growth.
As for taking cuttings, I look for short lateral stems tht will yield cuttings about 4ins long.
I try to take those side shoots as a heel - i.e. I gently tear the lateral off, so that it comes off with a little bit of the main stem.
If the heel is woody, expect rooting to be slow.
If its semi mature (not soft, not woody) then that to me is perfect.
I dont use rooting compound any more. I'm sure I should, but I'm quite happy with my success rate.
I put about 1in of the cutting into half compost (or peat), half hort grit.
I keep the pot out of direct sunlight for a week or more, in the greenhouse (which as you have said does get quite hot).