Hi Bee_C and welcome
You want to use something that won't mould but will keep the moisture in to maintain humidity.
Potting compost and 'normal' garden peat won't do. They keep decomposing and releasing nutrients which is good for plants, but suck for T's. Plus the mite problem.
Coconut husk peat on the other hand doesn't decompose, well at least not fast enough to be a problem, so look specifically for dehydrated coconut husk peat.
The blocks I buy have their packaging removed, so I had to do a bit of trial and error without the instructions:
What you do is get a big container (bigger than you think you'll need) break off small chunks. Slowly add boiling water and see the stuff come alive as it swells and expands! Don't add too much water. Puddles means too much water, and stir to get the clots separated. Let it cool.
Stuff's magic in how much water it can absorb, so what I do is get a large tray and tediously squeeze out handfulls so that it doesn't drip anymore, then spread it on the tray for a couple of hours to cool to room temp and dry out some more.
Don't worry about making too much. It's pretty cheap. I'd rather make too much than too little and go through the tedious hand squeezing again.
Hope this helps! B Albopilosums are the Best!