Depending on how dry the conditions a good soaking once a week might work for you.

You could also use the skewer method. If you go to your local grocery store you should be able to find bamboo skewers. Stick one in the pot next time you water and leave it there. Then after you water, you can check it every couple of days. Just pull out the skewer and place it against you cheek and you will be able to tell if the medium is dry or not. If the skewer does not feel damp, then water and put the skewer back in the pot.

Thanks! I have tried the skewer method but if I put it on one side of the pot it can come up bone dry but slightly moist on the other side (from the condensation and lingering dampness). I guess I’m just afraid of overwatering if there’s a little bit of moisture left.

If your mixture is airy and there are holes in your container to promote air movement, you won't be doing much harm if you water more often, as the water will drain out, just leaving the bark to provide high humidity. Though phals can tolerate it more than other orchids, I rarely let mine dry out completely. And if I feel the bark is completely dry, it gets a long soak in a bowl so it can re-absorb lots of water.

For me if the roots are green I don't water. If they are gray I water. Easy peasy!