To the exotic plant importer's dismay that gifted me "Cherrie", I use Miracle Gro Citrus, Palm, and Cactus potting soil on a bed of pea gravel, sitting on a screen covering the drain hole. I have been using Schultz Cactus Plus 2-7-7 food with the waterings.
I've also fed her Alaskan fish fertilizer, which she appeared to like and pumped out pups using, but switched after I was told that was all wrong.
The interesting thing is that she has forgiven me all my misstarts and foibles, as evidenced by her robust health and fecundity. Unless she is frightful of dying and trying to pump out as many offspring's as she can first....................
Have you seen the graft where they put a Williamsii button on the top of a St. Pedro for accelerated maturation and growth?