I'm doing a repair job for a friend Monday. She runs a beauty salon, and some of the plastic laminate on various counters and edges in her shop has come unglued. I've got contact cement (the good stuff, not the waterbased stuff) and have plenty of experience installing new Formica. But I don't know if I can re-glue without removing the old glue or not. I can scrape off the bigger chunks and any loose stuff, but I don't think I'll be able to get it all. Am I buying myself problems down the road by not removing all the old glue?