I’m trying the Model Master Acryl paint and no matter what I do there are always some residue left in the call of the cups of my badger 150 that I can’t get rid of it but by sanding the paint. I have to say that after I use one cup, I clean it with water and ISO but still some paint sticks to the cup then I left the cup in water until I finish my painting session and clean my airbrush but then still the paint is on and I can’t removed until the day after by sanding the interior of the cup.
Windex will get that stuff out with a bit of rubbing from a q-tip or a paper towel. Also, MikeV has a recipe for a custom acrylic paint cleaner he makes using windex and simple green and something else, I don’t remember the recipe exactly though.
you can also try fantastik or simple green to clean them, let them soak overnight if need be… it will dissolve… I’ve taken all the paint off a model with that before… also castrol superclean will work too… again overnight soaking will definitely get it off… by sanding your cups you might be causing it to stick worse now… if you notice it still does it you might want to order a new cup or two…
2 parts distilled water, 1 part Windex, 1 part Simple Green. It works great for me.
I use Model Master acrylics a lot and haven’t had that problem, but I seldom leave any paint in the cup for more than an hour or so. Does your paint cup have a cover on it? If not cover it with aluminum foil or something between sessions.
If all else fails try laquer thinner for cleaning the cup out.