I've been asked about my technique for this so many times that I figured it was probably about time for me to put something together. I strongly recommend this video by Ratfink. It's the one I used when I was experimenting with dye for the first time. So anyway, this is my feeble tutorial on how to dye figures and parts.
First, you should understand that dyeing is almost always going to be a precursor to painting, not a substitute for it. Anyone who has painted a joint knows that once you move the joint, you almost always have paint that rubs off, revealing the original color of the plastic. I have found dyeing to be a fantastic way to avoid having to paint joints. The color I most often use is black because it works well in the shoulder, elbow and knee joints of a G.I. Joe figure. No matter what color the rest of the figure is going to be, hints of black at the joints don't look nearly as out of place as say, red or white. Also, you will find that the dye will work better on the softer plastic of heads, hands, feet, arms and lower legs. It often works poorly on the harder plastic used for torsos and upper legs. But that's okay - remember, you're going to be painting. The dye is just going to reduce the amount required.
Next, you need to make sure you have all of the tools. This may
differ from one person to the next, but when I dye figures I use
powdered RIT dye, an old saucepan and a strainer. The dye can be purchased at most department stores for a dollar or two per box. I bought the strainer at WalMart for about $5. The
saucepan was once my wife's, but after the first time I 'borrowed' it
for dyeing stuff, she donated it to Our Basement Workshop. Isn't she
awesome? I also have a ratty
old towel that I keep on hand specifically for dyeing stuff. No matter how careful you are, you will make a mess. I strongly recommend using something to cover any counter tops that you (or your significant other) don't want permanently discolored. Also consider picking up some rubber gloves. They will keep your hands from looking funny for the next several days.
Frequently, the dye will not seep all the way into the joints, so you need to help it along. You'll want to prepare your parts for dyeing by moving all of the joints as far as they'll go in one direction. In the photo, you'll see that all of the arms and legs have been repositioned with their joints exposed. They will go into the dye just like this. After they've been dyed, you'll reverse the joint all the way in the opposite direction and repeat.
So the next step is to get your dye ready.
I'm not going to re-type the directions on the package - you're capable
of reading and following them for yourself. The short story is that you'll mix the powdered dye with very hot water. Some people will mix the
dye with hot water from the tap, but don't do it on the stove top. I have found that
the hotter the dye, the better it penetrates the item you're dyeing.
Therefore, I keep the saucepan filled with dye on the burner and adjust the temperature so that it stays just below boiling.
I place the first figure or part into the strainer and lay carefully the strainer
over the top of the saucepan so that the item is submerged. As each item comes out of the dye, you'll want to lay it on the folded towel. Better that the excess dye soaks into this than the counter tops. Trust me on this - I've spent too much time scrubbing dye off the counter tops and some of it never came off. This process is repeated/continued until all of the parts have been dyed.
After the parts have been dyed, I recommend letting them sit for quite a while. Not only will they be hot, but the dye will probably manage to seep inside the figure, so excessive handling will cause it to run out onto your fingers. The photo to the right shows the results of dyeing the same parts in black. Note that the torso on the second figure is a reddish color, rather than black. Also, looking at the four pairs of Cobra Diver legs, you'll see that the upper legs are still mostly red. Like I said, you will still be doing some painting, but now there is much less.
When all of the figures that these parts are intended for are complete, I'll post pics in this tutorial to show how they turned out. If anyone has questions on the process, feel free to contact me or (even better) leave a comment at the bottom of this post and I'll answer it publicly so that others can benefit from the answer.