At this point my small collection gets mostly watered together. I do have them grouped by light requirements, with the ones wanting higher light in the windows (I have a South window and an East window with large sills) and the lower light ones under lights. What I have done over time is to try to find medium that allow me to water together - every week or so they get a good soak and sometimes if I am in a hurry I just water them in place.
However, I am experimenting with S/H to see what will grow well for me that way. That's a whole 'nother ballgame! I've got the S/H crowd together in the window over my kitchen sink, so it's easy to watch them and see how they are doing and if I need to adjust my care. I've a couple of Catts that are doing very well this way and a few Oncidium alliance (NOID) that seem to really like it. Looks like I was keeping it too wet (or it was too deeply planted) for one tiny Catt start I got for free, so I pulled it and let it dry out... it came apart into two tiny starts! I put one back in bark and one back in the S/H with more care as to how it sits in the medium. Now I wait to see which way works for it.
My one little Masdevalia is next to the kitchen sink (I don't think it wants the South sun and heat, but I want to watch it). I water that one by checking it every day and deciding if its ready. I'm happy I've kept it alive more than a year.
I also have my Bifrenaria in a hanging basket over the sink. I water when it seems to dry out (I tell by weight). It's thriving, I hope it blooms some day! I saw a brand new growth just a few days ago, so cool!
I guess mostly I keep track in my head, only about 20-30 orchids, and I check them and talk to them a lot. For a long time I watered my Phals when my Pothos started to get wilty... hehe