If I want the quilt to have the crinkle old fashioned look I do not pre-shrink. If it is something like a table runner or I want to keep the flat appearance that I want to be flat , I always preshrink. I use warm and natural because it holds up the best to preshrinking. ( this is for cotton battings)
As was mentioned earlier do let it soak overnight to fully saturate the fibers , yep it floats , so you will need to reposition a few times. Do not agitate , just spin and put in the dryer.