Word of Mouth Marketing and a stringent marketing campaign to target all Velvet Revolver fans!
Any publicity is good publicity... this tour has got a buzz like nothing else, people speaking about GNR all over the place. I've even seen a couple of ads advertising the tour on TV over here.
It wouldnt take much to be honest. Normal avenues, TV, Mags, T'internet, Radio, billboards etc etc....
Its Guns N Roses. Nuff said.