well, i think i'd put them in a pebble tray of water. the way that works is you get a tray 1-2 inches deep and larger than the pot that the plant is in. then, you put pebbles or rocks (or whatever) in the tray, fill it with water, and sit the plant on the rocks so that the plant's pot isn't touching the water. then, when the water evaporates, it moistens the plant. those plants are used to a high relative humidity (80% or higher, sometimes 95% or even 100%). very few homes have humity that high ("comfortable" is around 60%) and during winter months, most homes are actually dry.