Rit and Tintex are both all-purpose dyes, too fade-prone to be worth using at all. If you want the best dyes, don't use these. See "
About All Purpose Dyes". (In Australia there is also a cold-water brand of Tintex which is fine, but the Tintex in North America is the fast-fading all-purpose type.) You can correct the washfastness problem with Retayne, but then you'll have more problems with light fading. It's better to use a high quality dye such as Procion MX dye.
Dylon makes a variety of dyes. Some of their dyes, such as Dylon Cold Dye, Dylon Permanent Dye, and Dylon Machine Dye, are fiber reactive dyes. They last well but are not very suitable for mixing your own colors. Dylon also makes Dylon Multi Purpose Dyes, which are just another short-lived all-purpose dye. Tie dyers invariably (so far) prefer dyes that are labeled Procion to dyes that are labeled with the brand name Dylon. See "
About Fiber Reactive Dyes".
If you use Procion dyes, yes, you do need to follow a good recipe, which will include soda ash. If you don't follow a good recipe, don't expect the dye to work. It's easy to use, far less trouble than using boiling water, which all-purpose dyes require instead. For recipes for Procion dye, see "
How to Dye" on my site and "
How to make a tie-dyed t-shirt" on the
Tie-dye Wiki.
Paula