Just curious: For what is it you use the mineral spirits that much? The oil painters in my group use sunflower oil or any kitchen oil to save their brushes in, as long as they are painting. They all state the brushes remain good and are clean. Only if they stop painting they use something else to clean them and if cheaper brushes are used they throw them away. I am the only one using oilpaint mixable with water. So the brushes are cleaned with water.

I wonder if the oilpaint itself isn't the problem too.

I never saw paper bumping using acrylics, neither cardboard, thise parts of boxes. After all those years (over ten by now) it still looks good. The same counts for what is used to paint on papier-mâché. I never bought the most expensive acrylic paint. I wonder how you used it to paint and about your type of paper.

$1-2 for one painting? If you ask me it costs more.

I love that worm!