When I am doing my figures, or anything that requires small amounts of acrylic paint, and don't want to use a wet palette, I lay out a couple of strips of masking tape and put my drops of paint on them. Not the Tamiya tape but good quality decorators tape (3M) and put the drops of paint on them, you can then thin the paint and mix and have a few different colours on them. Then when finished just peel the tape away and bin it.