I attached chicken wire all around the surface of my house. This I did with pliers by looping tie wire through the bags. The purpose of the chicken wire is to ensure that the mud won't slip down while I apply it or fall off when it cracks. Cracking is expected and is not an issue since this layer won't be visible when the house is complete. The main purpose of the mud layer is to fill the gaps between each row of bags. It doesn't have to be pretty, it's just to minimize the amount of stucco I need. I'd rather fill the gaps with mud because mud is cheaper to make.
For water, I bought myself a big water tank and called a local Mesa man to come fill it up. I myself don't have a membership to the neighborhood's water well, or a truck to haul water anyway, so I get my water delivered by someone who does.
I've seen people apply mud to earthbags with a trowel or simply by hand, which is the obvious method, but Atulya K Bingham wrote about throwing mud balls at the walls. I tried that because it sounded like fun, and unsurprisingly, it worked great! Better than any other method of application, and much more exciting. And for the hard to reach places, I didn't need a longer ladder, I just needed better aim. But my mud is mostly clay and very, very sticky. It adheres better to the hands than any other surface. Once the mud is flung, it's best to leave it alone. Any attempt to adjust or smooth it will only make it worse. And thus, I laid it on thick, unnecessarily thick, without spreading it out. In hindsight, I could have used a lot less mud by adding sand to the mix or using more water. That way I could've been more precise and efficient with my materials, but that is knowledge I hadn't learned until afterward. So I'll have to do better next time.
The next step was stucco.
Nearby is a dry river on national forest land that I was told I could go to and gather sand. So after a few expeditions down a few forest roads, two-tire trails through the sage flats, I found a route that goes down to the sandy bottom of the dry river's little canyon, full of sunflowers and smooth rocks, and tracks leading to where the good sand is. It's evident that this is the place. A free resource for sand!
And as for clay, I used my own soil. It has a high clay content. Any impurities are minimal and won't matter much anyway.
The first layer of stucco, I lathered on with my (gloved) hands. It created a rough surface, good for the next layer to stick to. For the second layer, I used a trowel to spread it smooth.
Hot tip: wet the surface first.
The first batch of stucco, I made with a recipe I found from a quick Google search (5 sand, 1 lime, ¼ cement) which didn't stick well and cracked when it dried. I nearly completed the whole first layer with this stuff before I got curious and started experimenting. Eventually I came up with the perfect mix (5 sand, 1 clay, 1 lime). The clay fills the voids between sand particles, and the lime's flexibility helps it stay in tact while drying. No cement! And no cracks! It's incredibly sticky, holds its form, and doesn't slide down the wall. Such a pleasure to work with.
Lime is more environmentally friendly than cement, and more forgiving because it doesn't turn rock hard immediately like cement does. It gives you more time to shave off unwanted globs and redo areas you aren't completely satisfied with. The only disadvantage to lime is that it takes much longer to reach it's full hardness. Cement takes two weeks, lime takes 3 months. So it's important to keep it safe from harm while it cures.
I was told not to underestimate the amount of time it takes to plaster the walls. I knew it wouldn't be fast. The work is much easier, yes, it feels like a vacation compared to digging and bagging, but it consumes a great deal of time as well. About half as much as creating the structure. It's slow work and it's not as exciting as watching walls go up, but it's important and worth the time it takes.