The hack
Send emails to makers who just launched their product.
Why it works
Makers are very receptive to all incoming communication. Imagine you've just posted what you've been working on for months. You probably going to read every email with a subject like: "Great work on the PH launch". If you’re selling something that makers need, this is an easy way to get to them.
How to do it
The manual way
Most makers have their social media or websites listed on their profiles. Go through them and find their email. As a rule of thumb go for people with just a few upvotes, they are the ones that will be the most receptive.
Read this for cold outreach copy hacks: 101 of cold email (beginner guide)
The automated way
There are a few tools that can scrape the emails for you:
They automate a lot of the manual work, but they only get around 30% of the emails you would get the manual way.
Also, it's not just indie hackers using ProductHunt, there are a lot of companies marketing their launches as well. You'll need to remove those manually from your list to only reach the relevant people.