Just curious how the fellow forum owners deal with open proxies and spamming trolls?

Make sure it's required to confirm email address upon registration. Many trolls don't like to register on forums where they know it's possible for their ISP to be contacted if they are bad. Also, it's very helpful to have a good team of moderators from around the world (ie different time zones), who can be on the site 24/7. Constantly, quickly deleting post after post by a troll will eventually cause him or her to lose interest.