Put water down, stuff cotton ball, add paint and use a paintbrush to push the cotton ball in areas the paint is, then stuff more cotton, more paint, letting the cotton ball soak up the paint. With acrylic, its a lot thicker and doesn’t flow, so you will need to add water and then move the paint around to absorb. I use the handle end of the paint brush to adjust the cotton ball on the inside and push the paint up the sides till I get the look I want.