Publicists?

Has anyone here had any experience working with a publicist? As a hybrid author with much of my work self-published, I'm beginning to think the only route to getting anywhere is to hire someone who has marketing contacts, inside info, and the like. I'm really at a loss as to how to find someone reputable who isn't going to charge me thousands upon thousands of dollars with little return.

Any recommendations? Words of warning? I'd appreciate anything you could share to point me in the right direction.

Thanks!