There are many ways to paint a guitar body, some are simple, some are multi-staged and hard to follow. I'm going to try to keep this tutorial simple and hopefully you will be able to paint your guitar body without wanting to kill me.
The truth is you should not expect your first guitar painting job to be any good. You might have to do it a few times before you get to the stage where you have the confidence to paint the body of a guitar you really treasure.
You can buy aerosol cans of paint for car bodies that will do the job on your guitar or you can buy guitar paint in cans that will duplicate your popular Fender or Gibson colors. You will do well to get a face mask and goggles unless you plan on your lungs and eyeballs matching your guitar. The alternative to cans is a spray gun in which case you will get a better finish that needs less sanding.