I've found bartering or asking for product support to be the easiest and least stressful. Things such as brake pads, race tires, a race shop (if you're fast enough, win, will earn them more business AND they like you). When getting cash, it changed things from a hobby to work.
Here's some information that I posted on my website (the resource is all about how to get into motorsports and related articles):
http://www.goaheadtakethewheel.com/a...ponsorship.php
It certainly can be done but takes a lot of work and time. The biggest advice I can give is to really sit down and think who you personally know, who your friends and family know, that might be able and willing to join in a partnership (don't say sponsor).