You can usually get Mary Ellen's best press at Hancock's for $4.99, far below other retail. Or you can purchase the gallon from JoAnns online when they have a 50% off coupon for really cheap. I buy the gallon and fill my small spray bottles. I keep on in the sewing room, one in the laundry room and one at the ranch house......As far as the use of it, it makes piecing so much easier, the pieces seem to stay together while sewing and it helps stabilize bias edges when sewing triangles, diamonds and applique.
Diana in Tx