Father-Son 1974 Duster Project

Another question. What is a good way to remove the remains of the old valve cover gaskets so the bits and pieces won't fall into the heads where the valve springs are?
the gaskets came off pretty well, but some material was left behind on the heads here and there. I am planning on being super careful but there must be some trick...
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Put rags in/over... Shop vac as you scrape.