You've got all the right ingredients. I'd take a couple of handfuls of the pine bark mix, a handful of the potting soil, maybe half a handful to 3/4's handful of the sphagnum (break it up into smaller pieces) and a handful of the pearlite, then mix it all together. After a good mixing, where the components are relatively evenly distributed, you should be good to go. The mix needs to be airy. Don't forget, the hoya is an epiphyte, so it needs air spaced in the soil otherwise the roots will smother. I've used a very chunky orchid mix on some of mine with zero other ingredients. When watering the water just flows right through so I need to water more often, but don't have to worry about drowning the roots.
After potting your plant, give it a good watering, saturating everything, then let it sit for a few days. Check the mix often and it'll tell you how fast it's drying out. If quickly, just water more often. At least you won't be over watering which is detrimental to good root growth.
I also feed mine a diluted orchid fertilizer about every other week. I use rain water for the fertilizer and even for just a normal watering. The plants love it.
You'll do just fine. It's the journey, not the destination that is important. Enjoy your plant and best of luck to you.
