Hire PAID posters to post up a lot of relevant industrynews links and comment on them. Hold contests Set up partnerships with established webmaster article sites.
Contests, and finding paid posters should be rather easy to do... I would suggest doing that. 10 cents per post is a pretty normal rate which most posters like, and new sites can offer without breaking the bank.
Why don't you start a contest? I'm sure you can afford it since you paid for the vbulletin license. Write some articles as well, maybe develop scripts, let your imagination go wild!
i think it is quite hard to have another successful webmaster forum. however, as mention in the previous posts, if you specialize on a topic, it is still possible. There are specilize forum such as link building / link trading. And you can also use those automated poster to make rss post into different category of your board to make it seems like there are activity going on...
Offer Free tools Offer free newsletters Offer CUSTOM/NICHE content (i.e, directories of info that webmasters want, or a webmaster directory or a link exchange directory or barter platform) Offer VALUE that can't be found at other webmaster forums