Now...I didn't come up with this mix on my own....but I got it from a brilliant propagator/grower of tropical plants.... Big R and #3 Perlite...just about half and half. Big R is a Soil Conditioner...redwood shavings...now I grow everything in it and love it. He has been using the same mix for 30 years...nothing speaks like success.
Medinillas are epiphytes, so they want a VERY airy mix...lots of water. Shade.
BTW... Big R is less than 9$ for 3 cubic feet...and good for all tropicals.... the price is TOO right. If you can't find it...I will get the name of the distributor off the bag....
