I don't think your first sentence really matches the rest of what you're saying. Obviously I'm not telling you to pull out your full spec and implementation ro

I don't think your first sentence really matches the rest of what you're saying. Obviously I'm not telling you to pull out your full spec and implementation roadmap to discuss with everyone on the street. But you should be willing to share the core idea in a way that anyone can understand. The "what", not the "how", essentially. You can always divulge more if someone shows interest in helping you out, but you have to garner that interest by being willing to tell them something.