Some Felting tips and How to's...
Put the garment in the bath tub with hot water some shampoo and baking soda and have a bucket ready with cold water. Climb in and start stomping around like Lucy did with the grapes. Or get an old fashioned washboard and a little patience it will felt. I got my washboard at my local hardware store for 13 dollars.
I actually find that it's not so much the heat as the agitation and shocking with the hot and cold rinse. Also the ph level makes a major difference in the speed of felting. Soft water which is like rain water is very acid and will not felt well. You are looking for hard water, this where the baking soda comes in, you want the ph level on the alkaline side.
For me this is the fun part of felting, it's more of an art than a precise science. I've never had the patience to make a swatch and measure and precisely predict the way a piece will felt. I find each yarn is sort of different and if I use the same kind of yarn I kind of know how it's going to felt. But I find it always felts more vertically than horizontally.