Grow them very wet with really good drainage.
In Nature Phrag. caudatum roots grow in living moss over dead moss on rocks. The roots basically stay within the moss. The moss gets a lot of rain and stays very wet. but the roots also have a huge amount of air space between the loose moss and drainage is extreme.
If you can manage to water several times per week grow the plants in very loose sphagnum moss. High humidity is preferred. The wind blows the plants enough it is almost impossible to photograph the flowers. light does not seem to be important, I've found them growing in crevasses under boulders with never any direct sunlight and other plants growing on top the boulders in full direct sunlight.
The moss root environment appears to be fairly high in nutrients based on associated plants. More than weak fertilizer is needed.