Recommendations for DIY Potting Media?

[realoldbeachbum]

There is so much conflicting orchid guidance on the internet nowadays. I only trust you, Orchid Board.

I have been using Repotme premixed medium. Now that I have 54 orchids (can't believe this addiction), I would like to prepare my own. I have mostly Cattleyas & Phals, with a few Paphs and Oncids thrown in. I am looking to mix my own Cattleya and Phal medium. All orchids are grown inside by Eastern window or grow lights. Any DIY media suggestions?

One more thing: What is the difference between Orchiata and Fir bark? They look alike to the untrained eye.

Any and all advice is appreciated. Thanks!