When it comes to volunteer recruiting, I tend to find it even harder. You can't just look for smart people who get things done, but you need smart people, who get things, who have and will give the time required. Expectation alignnment, and selective recruiting are even more important in this case, as the "payoff" is far more elusive, as is the structure by which most people will quit a volunteer position.
I've been senior staff at a fair share of conventions, and done other volunteer management, and my takeaways is that in this case, the best volunteers are the ones who are tapped on the shoulder by their brethren or the event coordinator themselves. I don't see wide-scale recruitment as the best option. Tricks in the past that have either roped me in or worked for me:
Promote from within - ie, draw from your existing base those people who are already motivated and capable. Frequent attendees, excellent volunteers - those are your best bets.
Power of the personal invite - have your current crew tap other like minded, similarly skilled folks on the shoulder. Maybe they are part of a similar but competing group, maybe they are just skilled folks you know from another place.
As important as recruitment is maintenance. Volunteers serve because the love it, and are passionate about the project... cause they certainly don't get paid! Be aware of why they love it, what they get out of it, and how to not step on that while facilitating a relief of any pain points. In most organizations I've worked in, paid or unpaid, the manager is 50% of the experience - if the head of everything is not an inspirational leader, you won't get the people you need for the work. After that, it's culture and job fit - people will keep volunteering when they are a part of something they like - the social connection is really important here.
As much as the focus seems like it should be recruitment and selection, I think you want to spend an equal if not greater time on whether or not you have an organization that the talented people you are looking for will want to be part of...