I would put them in a sink and do several water changes until the running has stopped, or pretreat with Retayne , using the small pan on the stove method. With Retayne its important to get the water to 140 degrees. To dry put them on a rack or use a hanger to air dry. Batiks are not prone to shrinking becasue of the hot water used to remove the resist in the dye process. I have not had a batik shrink ( and have used 100 of yards) .... but many many run particularly dark colors, and have purchased from all the manufactures , it is not isolated to any brand.
I would not use a batik with white without Retayne.