For my neps, I use a equal parts of long-fibered sphagnum, orchid bark, charcoal, pumice, vermiculite and just a touch of peat moss. This isn't all necessary, but I have bags sitting around, so I make up a little cocktail. But I always have a top-dressing, the top inch or so, of pure lfs. Since I grow most of my neps on open shelves under a grow light, I like the extra humidity a top layer of lfs gives.
An excellent easy mix is lfs and orchid bark, say 2 parts lfs, one part orchid bark (or perlite or coconut fiber chips).