If you use the MG cactus soil, add half perlite to it. And let the plant dry thoroughly between waterings.

Would regular miracle grow or Schultz potting soil work?

I would still add perlite to it.

Yes, just soil would hold water too long.

But don't most soils already have perlite in them??

This is what the seller told me:

We grow them indeed in cocohusk. Thats the best thing in a tropical country and they also root IN the cocohusk so do not remove when u get the plant.
In temperate climats u cannot use coco husk because it stay wet to long. Dont ming about the little thats left on the plant cause cocohusk dissolves in few months.

Hoya kerrii Splash should be treated as a succulent. EXTREMELY well drained soil, full sun little water. And once it start growing ad little more water.
Its an easy plant, only way to kill it is with to much water.

Yes they allready have perlite in them. And you can use them without adding anything. Just be sure to let it dry completely in the winter and when you water do so sparingly. You would be surprised how long some hoyas can stay dry for when they are not growing.

I let my lacunosas and nummularioides go 5 to 6 weeks without without watering in the winter. They are EZ plants and the soil can stay wet fora while when they are not growing.