It is important to talk specifically about acrylic as well, as this is a very popular material for this product. In order to shrink this fabric, you first need to place it in a lingerie bag (or some sort of similar bag). Be sure to tie the bag shut to ensure no air comes out. Then, just like the wool, go ahead and bring a large pot of water to a boil on top of your stove. Again, bring it down to a simmer after that.
However, instead of submerging the garment by itself do so with it in the bag. To prevent yourself from burning your hands, either put on some gloves or use a pair of tongs to lower the bag into the pot. Once you have allowed it to simmer in the water for around 40 minutes, you can then remove it and place it inside of a towel. With the towel, soak up all of the excess water that you can. To finish it off, place the garment in the dryer on the highest heat setting you have.