This might sound intimidating, but it's an extremely easy way to get really great looking fabrics.
As always, I'm going to assume you're familiar with preparing fabric, the basic supplies, and one-color baggie dyeing. If it's been a while, take a minute to review these.
You'll need two colors of dye for this lesson. My quilting buddies seem to like it best when I use colors that are next to each other on the color wheel, such as yellow and orange, or blue and green. What? You don't have two colors next to each other on the color wheel? Remember from your two-color gradation lesson that you know how to mix them from your primaries. But feel free to use any combination you want. (I did a peach and violet once that was scrumptious!)
Mix up a batch of each dye color, in any dilution you like. If you have urea on hand, use it in your chemical water to help keep the fabric damp while you're working. (Refer to your notebook to see how diluting the dye changes your results.) Prepare several (damp) fat quarters so you can try each of the methods that follow.
First, get out one of your 2-1/2 quart buckets, and put about 1/2 cup of dye mixture into it. Place a fat quarter in the bucket, and get it thoroughly saturated with dye. Leave the fat quarter in the bucket, lightly crumpled, and drizzle some of your second dye onto the fat quarter. Use as much or as little of the second dye as you like. Let sit 4 - 24 hours, then rinse and wash as usual.
For the next method, put a damp, lightly crumpled, undyed fat quarter in a 2-1/2 quart bucket. Drizzle some of each dye onto the fat quarter -- you will probably end up with some white areas of fabric. Use as much or as little dye as you like. Let sit 4-24 hours, then rinse and wash as usual.
For the last method, put about 1/2 cup of dye into a 2-1/2 quart bucket, and add a damp prepared fat quarter. Get the fat quarter thoroughly saturated with dye, crumple lightly, leaving some of the fabric above the surface of the dye. Slowly add some of the second dye to the bucket, but don't get it on the fabric. Let sit 4-24 hours, then rinse and wash as usual.
After you've washed and dried your fat quarters, compare each of the methods. You may find one is your favorite, or you may like all your results. Now try each of the methods using a 12 ounce drinking cup instead of a bucket. (Be careful not to spill the dye!)
You can also do larger pieces with this method. I find it's much easier to quilt a whole cloth quilt when I've hand dyed it with a couple of colors first -- the color gives me a starting place. (If you need to piece the muslin, do it before dyeing to make the seam practically invisible.)
There are lots more ways to apply two colors at once. I'll cover a few of my favorites in the "Getting Wild" lesson, but feel free to experiment. Try using the same amount of dye, but add more chemical water. Try using different tools to apply the dye. Try using rubber bands to scrunch up the fabric. Let your imagination go free -- the worst that can happen is you end up with a fat quarter that you overdye or use in the back of a quilt! (One of my friends once said "I learn something from everything I try, even if it's that I never want to do it again!" LOL)