I used to use the rooting powder for years and then I stopped using it overnight and noticed no change whatsoever in how my succulent cuttings root. So I'd say it is not needed in most cases and probably doesn't even make any difference, with very few exceptions among the more common plants in cultivation.
I usually leave cuttings in a bright, shaded place with good air flow for a few days to a week and then pot them up without watering. Then I wait another week or two before watering for the first time. You will want to wait longer when there is a lot of surface area on the cut. Some plants are so easy that you can pot cuttings up the day you take them. Waiting to water is the important part, really. And try not to bury a lot of stem. Like half an inch or so max works most of the time. Buried stem, beyond whatever is necessary for stability, tends to be an invitation for rot.
I have used neem and did not see any great difference versus dilute soapy water (which is what the neem is usually dissolved in anyway). My preferred insecticides are dilute soapy water (I like Safer brand, which sells a concentrate that I can dilute when needed) and 70% alcohol (which seems to last longer and work better than the undiluted stuff).
More about pest control here
The thread "Succulent Pests & Diseases" in
Cactus and Succulents forum
