I recently hired a hack plumber and one of his worst offences was dripping abs glue into a fiberglass tub shower unit in the basement while glueing fittings for upstairs drains. He then tried to wipe some of it up before it dried which failed so he put wood shavings and papers over that spot and left w/o saying anything. When I discovered it and confronted him he said he could get it but didn't say how and I don't really want him back on the job. The unit is a Lasco unit and is Ice Grey. What can I use to remove the glue w/o damaging the gel coat finish?