Here's how I did it. First I chose six colors of procion dye: Indigo Blue, Black Cherry, New Black, Lemon Yellow, Fuschia Red, and Charcoal Gray. I order mine from Dharma Trading Co. and have always had a great experience with them.
I used an old measuring spoon to scoop the dye powder. It's safest not to use any equipment with food after using it to dye! I didn't measure the dye, but the small measuring spoon fit inside the spray bottles so it made the process much less messy.
I scooped about 1 - 2 tsp of dye into each spray bottle, plus 1 - 2 tsp of table salt (this helps to fix the color). Then I added warm water, put on the lids, and had my helpers shake them up.
I used cotton jersey knit fabric, presoaked in a mixture of water and soda ash (one cup of soda ash per gallon of water). I soaked it for about 20 minutes before dyeing, and used the fabric wet.
I laid out the wet fabric in the shade and my helpers and I started spraying.
The particular bottles that I got dripped, which is what made all the spots. I love how they look, especially mixed with the airbrush-style mist the bottles make.
I started with the lighter colors and sprayed until I was happy with each color. I used the darkest colors next. I wanted to leave some white space and some lighter spaces on this fabric. After I was done with the black, I went back and added a little more yellow and fuschia.
I think it would be fun to try different spray bottles to see if I could eliminate the drips sometime. It could look really cool to just have an airbrushed look. I think wrapping a rag around the spray bottle, right under the nozzle, would help with the ones I already have, but they dripped so much, I don't think the rag would eliminate dripping. I may try bottles more like this next time. I use something similar around the house and they don't drip at all.
When working with procion dye, it helps the dye set if you keep it wet for about 24 hours. My fabric was large, so I folded it up and put it in a garbage bag. I tied the top and brought it inside. The dye will work better if you keep the fabric warm (room temperature will do).
The next day, I rinsed the fabric in the sink with a little Synthrapol detergent, then washed it in the washing machine with Synthrapol. This detergent is amazing. It removes all the excess dye so the fabric looks the same after washing as it does before. Without it, red dye may spread and make all the white areas pink. Black dye could make all the white areas grey, and so on. Synthrapol keeps everything where it belongs and takes away the extra. After washing with it, you can wash dyed fabric with other laundry without risking color transfer. (This post is not sponsored in any way. I just like these products.) I have heard that blue Dawn produces similar results, but I haven't tried it myself.
You can see below how bright my colors are and how white the white areas stayed. This is after washing and drying the fabric.
My plans for this fabric are to sew a Marianne dress (pattern from Christine Haynes).
Then I should have plenty of fabric left over for a second project, so I'll probably dye it again, using more dark colors (and maybe a different technique) to get a different look.
Have you tried spray dyeing? Do you think you'll give it a shot?