Paint Touchup

Do not thin the paint too much as it will change the durability of the topcoat. Buying a 2nd qt, gallon of flatter paint will also change the sheen but cost you more in the end and you will have a bunch of paint sitting around. The easier fix is to ask your local Sherwin Williams, Quals or other paint supplier for some flattening powder which is the only real difference in the sheen of your paint and the flatter paint suggested above and costs pennies. About 4 oz of this powder to a gallon will change a satin, eggshell to a flat. You could do the math and mix a small pint to test it. Good luck.

Read more: http://wiki.answers.com/Q/If_you_bought_a_satin_paint_to_match_to_an_existing_paint_but_it_is_a_little_too_shiny_can_you_add_something_to_the_paint_to_flatten_it_some#ixzz1iVG0z4u1