We can make this thread sticky if everyone makes an effort to keep the discussion on topic. I think there is a lot to be learned from the personal experience of the various members here who have kept succulents for a while. Thank you Bob for the initiative and for sharing what works for you.
I also use 70% alcohol in spray form as a quick and easy remedy for mealies and juvenile scale insects. I also use insecticidal soap (Safer brand), which as I understand it is just regular soap prepared with potassium instead of sodium in the base, in order to be friendlier to plants. I buy a concentrate and then make up what I need as I go. I think regular mild dish soap will also work fine at 1-2% in water if you use it in a focused manner and rinse thoroughly afterward the next time you water. It's the accumulation of sodium over time that will cause any problems, and that's something you can avoid. Soap itself (in reasonable doses) is pretty harmless to plants and their roots. One nice feature about the alcohol is that it will evaporate over time, and thus leave zero residue on the plant or in the soil.
I make a point to always spray when the sun is not out, so at dusk usually, or on a cloudy day. Part of that is to allow the product more time to work, and part of that is to prevent any kind of burn (which has never happened to any cactus or succulent that I have used alcohol or insecticidal soap on, and I never rinse until the next time I water).
I would also like to share some thoughts on mites and fungal diseases, but maybe it's better to focus on one thing at a time. The most frequent succulent pests here are mealies, hard scale insects, and aphids, and the two sprays I mentioned are my go-to first defenses when they appear.
