Just say the same thing each time with mime actions to match and they’ll soon pick it up
I was in our local chemist a few months ago and one of the ladies who works there noticed my dysgu Cymraeg badge and said her husband is a Welsh speaker, I asked if she could speak Welsh, she said a little bit, so when I see her we have a little chat lol
I was wearing a badge saying Dysgu Cymraeg about 2 years ago, I went into my local chemist, the lady behind the counter pointed to my badge and said Dysgu Cymraeg pointing to my badge, so I said that I’m learning Welsh then asked her “Ydych chi’n siarad Cymraeg” she replied typin bach, so we had a little chat in Welsh, it put a huge smile on my face as I’de lost my dad a few days before, but the funny thing was that I wasn’t in Wales but in my local shops in England
I was on the tube platform in London, wearing an S4C T-shirt, and a young man stopped me to ask if I spoke Welsh. We had a lovely chat! (He had done Welsh-language education, but then moved to London so didn’t get to speak it often.)