I bought some very dark green $3.49 or $3.79/yard flannel - the tag said double brushed. It felt a bit like felt before I washed it.
I soaked it in hot water in the washer for about three hours - turned the machine off and let it be (I forgot about it and started doing something else) - I washed it with a small amount of laundry detergent on a short gentle cycle and dried it till it was 'hot done' in the dryer.
The shrinkage was much less than I expected - about one inch in length per yard and two inches in width - and the surface did not pill. Also felt much softer and fluffier than when I brought it home. It did not seem to shed very much lint, either.
I was pleasantly surprised.