I've used paint a bit. If you go to the Dharma Trading site, there is a lot of info there.
I especially like Lumiere paint. You can purchase sample kits that give you small bottles of a number of colours/finishes so you can test them out. These are specifically fabric paint.
You can also use acrylic paint, mixed with a fabric medium. If you are doing a wall hanging that is never going to be washed, you can get away without using a medium, but I find it makes the colours flow better. If it is going to be washed, the medium helps the paint heat set so it doesn't fade as much.
There are lots of videos on Youtube on how to get started. I especially like On Point TV/Quilting with Nancy for technique videos.
Now, if you really want to go down the rabbit hole...look into monoprinting with gel plates. It's gorgeous.
Watson