JJ,
You missed it. There are two ways to get the valves at the right position to set the clearance. One is to turn the engine until the valve that will give a sum of 9 when added to the valve to be adjusted is fully open. So, for example, to adjust valve 3 you want valve 6 fully open.
The second system is to have pairs of valves "on the rock" to adjust a second pair. Those pairs are as follows:
Open valves ............................... Adjust valves
1 and 3..............................................6 and 8
2 and 5..............................................7 and 4
6 and 8..............................................1 and 3
7 and 4.............................................2 and 5
If you find any of those pairs on the rock when you start, you can follow in the order I have given them to adjust all of the valves. This minimizes the number of times you must turn the engine to complete the process.
Regards,
Paul