Sorry, just saw this.
4 ounces should be plenty to do a stock and handguard set.
"Usually" you have to only use one good coat, depending on what dye you use.
The solvent based dyes will dye DARK very fast so thin it and experiment on some white pin to get a feel for what you need.
As far as I know (Note the qualifier) the thinner for most of the solvent based dyes is denatured alcohol.
I could be wrong though, so to be safe you can just buy the Fiebing's thinner.
If you thin the 4 ounce dye will go even farther. I used some wool daubers to apply it. You can order them from Tandy, or just use a piece of cloth or sponge with rubber gloves.
Remember, the actual Russian Red is actually various shades of orange.
Here's my finished AK-74 Ironwood Designs laminated stock and the original Birch upper hand guard and European walnut lower hand guard.
After dying I used a couple of coats of Minwax semi gloss Poly. Gloss is too shiny.
The camera still makes it look redder then it is, especially the hand guards.