Best way to tell when to water is to do the weight test. Water you phal early in the morning and avoid getting water into the crown. Feel the weight of the pot. In a couple of days -depending on air conditioning , heat, etc.., lift the pot and feel if it is really light. If so, wiggle your index finger down into the bark mix and see if you feel moisture. If not, time to water. If it is still a bit damp, wait and check it the next morning.
Regarding fertilizer: We fertilize each week. The old saying goes "fertilize weakly-weekly.' Mix your balanced fertilizer 1/4 strength. Wet the orchid bark by running water through the pot. Next pour your fertilizer through the bark mix. Avoid the crown of the plant both times. Do this once a week. The next time you water, just run clear water through the mix. This will remove any excess salts that might build up from your fertilizer regimen.