Are there legitimate crowdfunding services that will work on a success basis? So, maybe a small fee up front plus a percentage if successful. Someone that will completely manage all the promotion so you don't have to do anything except answer their questions and maybe provide some raw content.
Short answer: In my experience, not good ones, unless you can be expected to be doing large numbers or they really love the product and are doing it more-so for fun.
Learn how to succeed on Kickstarter: here. Submit a free press release for your Kickstarter campaign here.