So, I can think of a couple ways to get extra light masking, but in the end the masking process is labor intensive no matter how you slice it. The nature of the beast.
Option 1 would be to buy light tack masking, then further de-tack it if necessary by repeatedly sticking it to a cotton cloth. Each time you peel it away from the cloth it’ll be a bit less tacky.
This is not a great option at scale for lots of reasons.
Option 2: make your own water soluable liquid mask. I’ve used wood glue as a mask before and it’s great. You’d want to thin it way down to work in a spray bottle but I bet it would work.
In theory you’d soak the final pieces in water and the glue would dissolve. Combine with an ultrasonic cleaner and I bet it’d work. You’d need to be sure your paint completely dried first but in theory… maybe?
Option 3: liquid masking is a thing in the art community. Surely there’s a water soluble option? My initial search didn’t yield any results. Hmm.