Yes you can get a lot of traffic from forums via the signature. But that will all depend on how much value you're adding to the forum. Posting one liners like "I totally agree
" won't get you the results you want.
Don't focus on making too many posts or threads, focus on replying to questions that you have more knowledge about where you can offer the most amount of value. Instead of making tons of useless posts on a forum.
The number of posts don't matter, but what matters the most is the quality of the posts you create. It's all about creating an impact with just a few posts. That will also help you focus on other marketing strategies or target other forums as well.
You don't need to rely on answering questions only, create a value thread that offers value (more like a blog post), don't promote anything simply offer value and those who like the article will most likely click on your signature.
The great thing about creating a value thread is that the moderators may like and find it useful for their audience and make it a sticky post, that's free traffic for a lifetime.
Does signature help me increase sales and drive traffic to my blog site?
Yes it can help you increase blog traffic and get more sales when done the right way because your target audience is already there. Simply focus on offering value and do this as a long term strategy. Pick a few forums that you want to target, after a while filter them out and focus on the few that bring you the most amount of traffic.
Hope that helps.