Step 3: Soak fabric in dye
1 table spoon procion mx powder
6ish cups of water. luke warm.
a tablespoonish of salt
in a bag or bucket. shake or stir.
Consult packaging for exact quantities. Though experimenting will provide you with more flexibility in the future. The packaging doesn't know your goals, anyway.
I often resort to a large zip lock bag, but the mop bucket is a more environmentally friendly container if you're not going to save zip locks (if you do save them make sure to label them as NOT FOR FOOD, especially if you live in a coop like I do).
Fold/rubber band/tye fabric if dying with a pattern. I like to scrunch it up to get the crushed look in the pictures. No ties or rubber bands-- the key to crushed is to let the bag sit still and not move the dye around. The uneveness of the soda ash, salt and fabric layering and squishing will give the crushed effect.
On the other hand, for even color use a bucket and stir consistently. You can even put a large load in the washing machine.
Put the fabric, eg a shirt, in the bag/bucket. Add more water if necessary to cover the fabric. Seal the bag (if applicable) and squish out the air.