About the only way you could make any money selling instructional materials at a major event would be to have another, bigger vendor carry your line for you for a share of the fees. Setting up your own booth just for lessons and DVDs would be a pretty big gamble just to break even.
Everyone uses a system. Everyone. It may not be something you can't accurately describe, or it could be a system recognized by all. There aren't gunsights on the balls to aim with, nor are there gunsights on a car...yet you can "aim" both to go where you want them to or to miss things you want to miss. Before feel/touch comes into it, you have some way of visualizing the alingment you need and accounting for things that would make your CB not hit what you want. You can sometimes see it in a player's PSR, often times not. Players often "discover" or are shown a new way to perceive the shot and a method/technique for percieiving, aligning and executing the shot, taking new variables into account that they didn't before and taking care of the other variables...and often that makes them more consistent. What many on here would call a "system" is just a simplified, consistent approach to the shot, taking calculation of variables out of the equation...because humans tend to over-complicate things. How often have you missed a shot because you were over-thinking it? "Think long, think wrong" ring a bell? Systems help you put the small variables into your subconscious where they belong...we all have a system, some do it better than others.