http://www.youtube.com/watch?v=YoGl00gysD4
Although it can be done without the tool, I think it is easier with it. I had the guy at the machine shop do mine when I had the head off since he had more experience with it. What he did was use a shim that was too thin and measure the clearance with the feeler gauge and then remove the cam shaft and repeat for each side. I also had about 20 extra shims to work with that I had collected. When you do find the sizes you need they are about $10 a piece from toyota.