I’m not deaf \ dumb but recently I watched with concern two middle age D\D people being given problems by a pub crowd!
All they had done was wonder into the pub looking for the toilet! Fortunately a man who did know interceded on their behalf (myself and others initially trying to help as well).
The landlord, bless him, when arriving from another part of the pub, & it explained to him, promptly threw the guys out who had started it!
What’s the easiest way to start, learn it!
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Deaf sign is taught in continuing education at many community colleges and recreational ed programs. The basic signs can be found on line with little drawings. And you might look at Galladet college in Washington DC to see if they have online videos.
Remember that deaf can always write notes.
I would go to my local school for deaf-mutes. There is a specific sign language for every spoken language.