Grow popowii like a multifloral paph, though a little wetter in the warmer months wouldn't hurt. In other words, it'll appreciate fairly bright lighting and good airflow, and the potting mix should be allowed to dry a little bit between waterings.
Schlimii can be grown wet, either watered frequently or allowed to sit with a small amount of water in the saucer. Otherwise, grow it in a bright-shady spot, more like the amount of light you'd provide a parvisepalum group paph.