How do I know when my bark mixture is dry and when to water

[adelong5]

Hi my name is arielle and I am having a hard time trying to tell when to water my cattleya and wilsonara. I know that the wilis needs watering similar to a phal, but the cattleya i'm not so sure about... The mixture they are potted in is more bark chunks rather than the finer mixture my phals are in. I can see if my phals mix feels moist with my fingers, but not the chunkier bark mix. Does anyone have any sugestions? thanks arielle