I had a print shop show me a pretty cool trick.
I always left my registration marks open so I could print them on my line up first print. and then when I was happy with the registration I would tape them off. Sometimes I would forget, lol. I am sure you have too. Then you need to use the spray gun to shoot out the ink on the good shirts that you forgot to tape the reg marks off on.
What I do now is align and center one of my films to the platen. stick it down just enough so it doesn’t move. Usually the little bit of spray adhesive from the last job is just enough so the film doesnt move but won’t be too much to make a mess of the back side of the film possitive. Now I go ahead and register all my screens to the film looking through the screen, you can actually still see on the screen where the reg mark was bunt into it, even with the liquid blockout. The cool thing is, you don’t need to worry about forgetting to tape them off before you start on the customers shirts.