Despite the misconception that a lot of folks have about the difficulty of getting the same color or good color saturation when dying your own materials, it is really very easy to get the shade you want and to reproduce it at will. The use of good quality acid dyes and putting Synthrapol in the dye bath are the two main keys to getting the color you want and being able to reproduce it whenever you wish. To check the color of the dye bath, simply put a small piece of a paper towel in the dye bath, dry it with a hair dryer, and voila, you know what color you are going to get with a quality acid dye. And the Synthrapol (a dye disperant that makes the dye evenly dispersed throughout the dye bath as well as a detergent to keep oils from preventing the dye penetrating the material) is needed to prevent uneven dye penetration and streaking of color.
AS you have already found out, RIT is not a good dye for hair and feathers. Before someone takes me to task for making the last statement, I am aware that there are many who use dye and that A.K. Best recommends using RIT in his book on dying. And yes, you can use RIT dye and get an acceptable dye job; however, you have to use a lot of RIT dye to get consistency in color (this is because it is a so-called union dye that can be used on proteins and cellulose and polypropolene and nylon and polyester, which means it is composed of several different types of dye). And RIT does not give you the nice bright colors that steelhead and salmon fly tyers are looking for.
Another reason many folks think dying is difficult and hard to reproduce the color is because they have used Veniard's dye (yes, I know that A.K. Best talks about using it in his dying book) and with very few exceptions (hot orange, kingfisher blue, scarlet, lemon yellow) all Veniard's dyes are mixtures of dyes of different colors. This causes problems with color consistency because there will be differing amounts of the various colors of dye any time you measure out some dye for use. And you cannot overcome this problem with shaking because some of the dye colors have different specific gravities that cause them to sink to the bottom of the container when shaken. Veniard's also combines acid dyes of different types to create some of their colors, and these different types have different melecular structure (some some, some medium, some large) that enter the material you are dying at differing rates, and this can and does cause uneven color saturation, streaking, and blotchiness.