Even 10-15 years ago it was hard to get sponsored. I was in the business so eventually after having a booth at a lot of shows, I started seeing the same people. Then it was easier to get parts and work done. Also we had "resume's" for the shop cars which included shows they had won, shows they would be attending, pictures, coverage and so on. As time went on, it got tougher and tougher for a lot of people because so many kids would take a bunch of sponsorships promising they'd be featured in some magazine, build the car and then sell it without attending any of the required shows or getting the features promised. I remember having to show written proof of a magazine shoot coming up before they'd send the parts and then after the feature came out, I made sure to send copies to the companies showing that we had mentioned them.
I can only imagine how hard it is these days since the recession and the industry is entirely different. As others have said, it sounds like you need to do a lot more before asking for sponsorship. It's not a win-win if you get free parts and they get mentioned by some kid with an almost stock car at a local meet...