How do I pitch in Facebook Groups as a newcomer?

On the advice of fellow Indie Hackers, I am trying to build a waitlist to launch to ahead of releasing a product!

I put together this Product Hunt Ship page (and I’m even tracking clicks too!). Now the only question is how to give it to people!

We want to launch to startup founders + entrepreneurs, but apart from posting on IH (where's everyone's super friendly), it's feeling really awkward to just start dropping our link into Facebook and LinkedIn groups. Even moreso on slack and Reddit!

Any advice? Is it okay to just drop in and pitch?