Most people have a fixed image of what selling yourself looks like: overly confident suit wearing people with nothing behind it yelling empty slogans at evetybody and their mother unsolicited just to see what sticks etc.

That is false. You can very easily sell yourself without ever lying or overstating anything. If all you have is a small CLI tool on github, selling yourself could be as simple as posting the link to the right people. Selling yourself could mean going to some event and talk to likeminded people, it could mean explaining some person what you are doing etc.

It is not about overly praising your own stuff — it is about not underpraising it.