And now, a word about water...
These days when I paint with acrylics, I use very very little water. I have a tall plastic container that I put about 1/2 inch of water in the bottom of, to keep my brushes wet and to rinse them. Before sticking them in the water, excess paint can be wiped off the brush onto another surface. Not necessarily a paper towel. It can be wiped off onto a separate canvas, to create an undercoat of color.
When the water gets dirty, I use a paper towel to soak it up. Then I hang that out to dry, and it can be used again for the same purpose even though it is stiff. I suppose such paper towels could be used for a collage purpose, but I haven't tried that yet.
If I want to get my brush really clean, I spritz some clean water from a spray mister into a little tray and rinse with that, sopping that up, too.
That way my sink doesn't get stopped up, and the acrylic paint doesn't get put into the water system.