I did at least 500 tails last year, most for me but some for tackle shops to sell use also. if you are just doing a few for your purpose, the rit is OK to use.
I have used Jacquard acid dye also. My Dad used that all the time when he did it with good results. He passed away and I took over the business, and now I am using a what I think is a better dye. I use a company called Pylam products. They make what I think is the brightest colors on the market, and the color last longer in the water. It is a little on the salty side for price, but when selling and trying to keep a reputation, I went for the better dye.
If just doing for yourself and only a few tails, the rit is the way to go IMO.
I buy my tails already dried, but with the price jump I have seen this year, I may be doing some myself. Here are to links to check out from another forum, skip some of the post to get to the one with the good info. One even has the way to use Rit dye. I suggest not taking your water to boiling, you can end up with hair soup really fast. I keep the water between 180 and 190, use an outdoor turkey fryer set up and do 10-30 tails at a time. Hope this helps.
Bucktail Preperation? - SurfTalk
Dyeing Bucktail Hair - SurfTalk
Winter Project - Processing Bucktails - SurfTalk