I've never applied a fixer and I use it in the washing machine.
I mix the dye bath on the stove as instucted then add it my washing machine (set on lowest level, hottest h2o, gentle cycle) and mix it up really good. I then add my fleece. I let the cycle run for about 3 minutes, stop it for 6 more, then let it finish. I air dry the fleece.
It works well for me.
I tried RIT on the stove top, but my vat was too small or something. I got a little uneven color in spots and the shade varied a little from beginning to end. (I cut my fabric in to 3 large pieces for head/neck, body, everything else (arms, ears, nose..)) It was pretty, but not what I was after.
The acid dye is easier. You just add it to the h2o, add vinegar as instructed, mix well and add fabric. I don't remember specifically how I time the cycle, but I have it written down. (i.e. keep good notes)