I ran my swatch through the washing machine one more time – this time I just tossed it in with a load I was running. There was a lot more stuff in the washer, so the agitation was better I think, and it did felt down a bit more – from 9×12 to 8x11ish.
The stitch definition is still there, but not as noticeable at all, and gone entirely around the edges and corners. I also discovered why you put felt in a pillow case — I took it out, and my lovely blue swatch had picked up a lot of pale white fibers stuck all over it. They trimmed off readily enough with scissors though.
Knit-Write 
I bet it’s thick! The zippered pillowcase is good for protecting the fiber and for protecting your washing machine motor from fiber clog/death. I have a pair of sacficial jeans that I always use for felting – they don’t shed a lot of lint (which I still worry about even tho the item to be felted is in a pillowcase).
It is very thick – it’s a nice felt, and will make a great mug cozy when I work out the pattern/proportions for it. I need a zippered pillowcase! Part of reason I opted to not use it was because of how much trouble I had getting the knot out of the one I used before. *laughs*