Actually being there and seeking out people who only speak Greek, will help you immensely. During a conversation, you will be forced to dredge up ANY words that you know in order to get your point across. “Sign” language helps, as well as a good mutual laugh when the going gets tough. I once had no word in the spur of the moment for “refrigerator” when presented with an elegant and quite perishable gift, so I said that we had «κρύο στο δωμάτιο» (cold in the room) which was well understood, but mutually VERY funny at the time! I have poured through books and language apps. In the past I’ve brought “cheat sheets” for phrases that I know that I’ll have to use (ie. dining, hotels etc.) but the things I remember best are when I am speaking with a non-English speaker. As mentioned before, you might find such people in non-tourist areas, the villages, or even in the cities, connected with family-run operations in which not every family member speaks English. I really applaud you for wanting to preserve your very special heritage. Your effort will definitely be noticed and appreciated. Καλή τύχη!