Hi Annette,
I use ordinary cactus soil and adding some perlite when I repot, but lately I have been mixing some akadama and kanuma with it. But not always, as they are a bit expensive and I only get little baggies of it. I like adding them though because they change color when wet, so it makes it easy for me to gauge if the soil is still wet and their size is like little rocks that can hold some water but releases them quickly too, allowing good drainage. This is with the regular succulents and cacti. But for epis, I add some fine orchid bark mix and the usual cactus mix, so there is a bit more water retention.
One thing I have learned, is to use shallow and wider containers for the succulents, unless they have really grown to specimen sizes that really needs a bigger container. It helps to make the dry out process faster. If I run out of shallow containers then I add fillers below so that it will not be using too much soil that may prolong drying time.
