I think forums can be key to developing and rounding out your personality. Which can lead you to extrovertism because of your personality. But also build up how the process works in your brain.
I'm a fan of online games and while I'm having fun, and talking to a lot of people my brain is processing other things that are going on. I notice there's hermits, introverts, extroverts in the digital world too and the principals are akin to the physical world.
The hermits aren't talking to anyone, trying to keep attention away from themselves, and ignoring people. The introverts don't talk much and are usually stuck to a circle of friends in the game that they only talk to. Extroverts talk to everyone, and make friends with everyone.
So the more you talk on forums, the more people you'll probably be talking to and getting to know. Eventually you'll just be a digital extrovert, and find it child's play to find someone to talk to and make friends. It all works the same in the physical world from my experience and what I see. However practice in the digital world will not help you in the physical, I think it rather accelerates your learning there since you understand the process now and may not be so fearful of it.
Just listen to people chatting normally. How people start up small talk to break the ice, and get into much bigger conversations from there.