I have a top loader. When I want to pre-shrink a batting I fill the washer full of hot water, turn it off and put the batting in. You'll have to push it into the water several times to get it all wet. I let it sit there ten to fifteen minutes and then turn the washer to spin. Once it's spun out I put it in the dryer on warm. You may have to pull the batting out of the dyer a couple of times and rearrange it so it all gets dry.