here's what I found on a web search (I'm dealing with same problem, how to remove the glue......)
Someone on the boards was asking about removing Wonder Under from her ironing board cover. I found these instructions from the University of Nebraska.
Removing Fused Interfacing
To remove interfacing that has been fused in place, hold a steam iron over interfacing for 5 - 10 seconds. Immediately peel off the interfacing. If it is still adhered, set the iron on the interfacing, but do not use pressure. To remove any fusing agent that remains on the fabric, cover it with a damp, lightweight fabric scrap and press. Peel off while warm. Continue with new scraps until all the adhesive can be removed by sponging the area with rubbing alcohol--but be sure the fabric or dye will not be affected.