Jacquard dyes are some of the best acid dyes available and ones that I use quite a lot. The Weaving Works also carries Synthapol, which is a cleaner/degreaser/dye suspender that will let you produce nice clean, evenly dyed materials. Depending on the color orange you want, Jacquard has several different shades: Fl. Orange is color # 606, which Jacquard calls Dark Orange. It will five a very nice, bright hot orange color.
Another excellent dye is known as Fly Dye and it is made by Organic Dyestuffs; but it is sold in 1 once containers for fly material dying and uses common fly tying color names for the colors. A quick internet search for Fly Dye will get you theri web site.
When dying, use about a 1/8 teaspoon of dye to a quart to a quart and a half of water that is not quite boiling and make sure you use a stainless steel bowl, pan or pot to prevent the dye from reacting with the dye pot, which would change the color or create blotchiness. Add the dye to the water then put some Syntrapol (about a 1/4 teaspoon) into the dye solution. Lastly, add a cup or so of white vinegar as the acid for setting the dye. Put your tails or whatever hair or feathers you wish to dye in the above described dye bath and let them steep in it for about 15 to 20 minutes to thoroughly dye them. Once they are the color you wish, simply dump the whole thing into an old colundar and rinse with luke warm water.
Dry the tails (or hair or feathers) by laying it out on newspaper overnight or through using a hand-held hair dryer.