You certainly need a better methods. Nowadays 90% of the forums don't allow affiliate links anymore due to the amount of spam.
Even if they did, I highly doubt you can make a sale by just posting the link on the forums. You need to drive highly targeted traffic to your link. If you don't target an audience who's really likely to have interest in what you're selling, even posting your link in a thousand different forums won't help.
My advice would be making a keyword research and creating YouTube videos in order to promote your product. Creativity is the key to everything in internet marketing, and combined with YouTube, you can make a massive amount of sales.
Good luck!