Similar to the method Judy wrote about, Sharon Schamber also does a method where you machine baste around batting using water soluable thread, trim, then put your quilt sandwich together and quilt.
This method has the added benefit of having you already having a line of stitching to follow---or improve on in my case
---.
In the class I took with Sharon, she had us bring wool batting to use for the trapunto. It was my first time using it and it was just luscious !
Sharon generously shares many free videos about her techniques. You can look around at
http://www.sharonschambernetwork.com
HTH,
Sue