My mix is 50/50 rinsed perlite/LFS, to which I add a tablespoon or so of laterite along with a couple Tbsp. coarse silica sand. I usually topdress with laterite as well, but the topdressing on the D. darwiniesnsis (and the hybrid of it) is coarse silica sand since I am presently out of laterite.
(Laterite is a great addition for Drosera mixes, in my experience. It can be ordered from dealers of tropical fish and supplies, but it is a bit expensive as a pure potting media).
Since my plants insist on a dormancy despite my best efforts to prevent it, I make sure I can provide a very light airy substrate that I can easily control the level of moisture in: too wet and they rot, to dry and they do not return from dormancy.
Thanks for the nice coments: these plants are among the darlings of my collection. I thought for sure the D. darwiniensis and the hybrid were history after this summer.
No seed has been produced by the hydrid, although pollen donated from it did fertilize my D. paradoxa. So far the resulting seed has not demonstrated viability, but my skills with Petiolarix Complex seed are not good (or else the seed I have gotten in the past is inviable). I am about to try another batch of the hybrid. X X X