Not as easy, as said. Mainly because it's not you talking about your productsy but others. So to start spreading word about your product, the others need a reason for this.

If your product safe a ton of pain, or resolving something which is a pain in some eyes, then it will spread by itself.

You can also act like a 'customer' and wherever possible just write a short sentence about it. Think of how a customer would talk about it. It's not meant like presenting the top features while you're writing how it helped you. Think of changing the roles with a customer.. what would the customer write/say.

So, by that you can do 'adverts' without actually doing it.

Search for communities, forums, groups.. that are on topic. Who would use your product? Go there, where such are gathering.

For example, doing grill accessories, you would tend to place your message into grill forums, not into football group. Except you see that someone is having a problem or asking for an advice for something... You could answer 'im using xxx. That helps me. Bye.'

Something in this sort of.

Have a product good enough that users want to talk about, nothing more nothing less.