Hi & welcome!
A schedule like that can do more harm than good since it's impossible to predict how long it will take your plants to dry out, which will probably fluctuate with the seasons/weather anyway. Water when dry is a good starting point. Both plants are types that don't wilt, but the leaves will lose their turgidity and become soft if too dry. The epiphytic cacti like Selenicereus are cacti, but from rainforest jungle, not dry desert. Letting the soil dry is a good way to prevent root rot if using potting soil made up of tiny particles. The soil type/texture will determine how moist the roots can be w/o rotting. If it's more chunky/porous/airy so that roots have plenty of oxygen while moist, not drying completely should result in the best/fastest growth. There are a ton of pics under the info part, in the database entry Lin pasted above.
(Lin, your plant is gorgeous!)
