I think that the key to getting quality dealers to setup is to talk frankly with them about what your intent is and how you plan to drive paying customers their way. That's the bottom line for them. From a vendors perspective, I think most dealers wouldn't care if it's a Wannenmacher show or some new 100 table show in the VFW hall as long as they do well at the show.
For starters, you can tell them about the hoardes of willing customers on OSA who have all but written off gun shows because of bad experiences in paying too much at the door (or getting the 'new' price once they get there), finding out the show is 50% guns AFTER they've paid and are inside, etc... let them know how you're addressing those issues and specifically targeting people who normally wait until the Wannenmacher show or just don't even attend gun shows at all. Do just like you said and ask them for a chance to setup and see how it goes... trust me, there are a lot of dealers who will be happy to give it a shot and see how it goes. If they make good money and/or buy good guns, they'll be back.
OH... sometimes the little things like having a coffee pot, cups and donuts for the vendors in the mornings can go a long way too. Hell just being personable and nice to them can go a long way. Don't know if you've considered it or not, but finding a few high school kids who will be available to help vendors load in and out for a few bucks might be a good thing. Security is a big deal too so make sure you have a solid plan outlined for them.
