Johnson outboard timing adjustment?

I have been searching the internet for instructions on making timing adjustments and every posting says something completely different. Some say you must buy some Special spark sensor thing that lights up markings on the fly wheel. Some say you must buy some kind of Special caliper that screws into the sparkplug hole. and others say just twist the idle adjust screw. My question is do you use the idle adjust screw and if you do why dose it mader where the markings on the fly wheels are. And what specal Secret classified information is in the shop manual that i must know. And what is all this stuff people say like "set it to 4 degrees". If there is no lodgical answer for any of these questions can someone just explane the flywheel markings and how to adjust. and are there any special tools i need?