You might get away with just mentioning your product in these forums, but also mention that you are related with the product. If you are humble enough and the product really fits the audience of the forum, you might generate some interest. And you don't need to fear any backlash from somebody uncovering your astroturfing.

That's what I've done with Dead By Zombie. So I don't truly astroturf. But I do chime in. I believe the guy behind Balsamiq used this technique when he was just starting out. Making comments and doing mini-pitches in various web forums that had the demographic who might be interested in his new tool.