I also use Hobbs 80/20 and depending on the look I want I may preshrink my batting. However, do NOT pre-WASH as let it agitate in the washer!! (Ask me how I know!!) I put my batting in washer & fill w/hot water; poke it down in and let it soak with the washer lid up. I then spin the water out & dry in a hot dryer. Hope this helps.
Polly