Respectfully, I think you're looking at this from a bad angle. You wouldn't go up to someone in the middle of a set, wearing headphones, and ask them to stop what they're doing to help you. Instead, you find someone who's finishing a set/exercise and politely say something like "hey, I'd like to try this exercise and you seem to know it well, would you mind taking a moment to give me a hand?".

I've personally done this twice this year (I genuinely wanted to learn, I'm not using it as a strategy) and it worked very well. I suppose culture plays a role but I'm in one of those countries where people don't usually socialize with strangers and it still works.