As for "step by step" directions, I did a Google search found too much information and jumped in. You'll need: a pot big enough to hold the part(s) in question, tap water, dye, electrical tape to keep dye from dying portions of the part you're not looking to dye (the tan in your camo pattern?), tongs to fish out the parts from the water, and paper towels to avoid dying the counter. A note to your wives, the dye will not hurt the pan or ceramic tile. It probably will stain a stone or synthetic counter top, an will stain grout.
1. Wash the parts in hot hater (use soap if you want). Rinse well. If you are going to a pattern, dry the parts and mask off your pattern. Remember to go light to dark. You can make the part darker, but you cannot lighten it. It's a one-way process.
2. Put water in a pot (I used a 3qt pot). Add dye until it looks a hair darker than you think will work. Heat the water. The first time I used a thermometer and brought the water to 170º F, the second time I brought it to a boil and backed off a bit on the heat.
3. Dip the parts in the dye mix. I tied mason's line to the first batch and used a wooden spoon to suspend them in the mix. Dyed a wooden spoon purple in the process. The second time I used tongs to grab the part (Magpul MOE stock and trigger-guard). Your choice as to how to get them in and out, wire would work too.
4. How long in the bath? Depends on what you're trying to accomplish. The first batch was in for a minute or so when I asked my wife if it looked right to her. The ended up in for another minute. The second batch I dipped 10-20 seconds until I thought they matched the first batch parts.
5. Rinse with cold water (to stop the process) and dry the parts.
I don't have anything to dye currently, or I'd take pics of the whole process in a step by step manner. I just followed others, using them, as a guide, though not necessarily as "the way" to do it. I'll be the first to tell you mine isn't "the way" just "A" way to do this. There are tons of tutorials out there, toutube videos too.
The parts before...
a better color representation, Magpul FDE...
the parts after (accurate color). Of note, the follower did not take color. I had it in the bath for over 10 minutes.
In this pic is by Spikes before BAR rail and my feeble attempt at camo. The colors aren't quite right though, but close enough. Really just a test on a spare magazine.
Hope that helps.