I used to be afraid of using the washer with this, but it seems to work quite nicely. The darker colors requier a double batch of dye. Just follow the direction on the package or bottle, making sure you have salt and bleach on hand. Salt helps soften the water and the fabric to take the dye better and the bleach is for cleaning out the washer immediately after you color your fabric.
I did the browns this week and tossed in an olive skirt that was faded and it turned out a nice chocolate color. Cotton works best to take the color and some synthetics don't work at all.
If you've got some cotton muslin fabric you can color it before making a skirt out of it. See what a little creativity can bring to your life.