ENTWINEMENTS

Folding origami is the easy part. Dyeing it is the hard part. Getting dye thru all those layers is the challenge.
Dyes have different ease of penetration. I percieve the penetration to be the highest with fiber reactive dyes , so in orger of decreasing penetration

discharge (sulfur dioxide, a gas)
fiber reactives
acid dyes
indigo

My theory assumes that larger molecules penetrate less. Even so the book shows that good penetration can be achieved with even indigo. How do they do it?

First they buy ready-to-use indigo in a bottle:

Aren't you a wee bit jealous? I'd love to buy ready-to-use indigo.

Then they place the tied cloth in an appropriately sized plastic bag:

Then some ready-to-use indigo is added to the bag:

The air and blue indigo are removed from the bag and then the bag is clamped shut. This is the critical step-- having the bag totally filled with the indigo bath and no air. Here is another picture of a larger piece: left: expelling the air, right: then clamped.

Once you have the bag sealed, you can then massage the wad of cloth inside to increase the penetration.

This way they have achieved good penetration on dense cotton with even indigo.