Hi Tamara, we have been growing our Promenaea on the end of the bench half covered by the phals that tower over it. It is growing in small bark with some moss to hold in moisture. The pbs are very 'full' looking and appear more round, so it seems to hold water on its own.
Ours most assuredly drys out between waterings. I don't know if this is the 'correct' culture for these little ones, but it has bloomed two years in a row now for us. We never mist, just water twice a week during the warm months and once a week during the winter months.