Valve adjustment

Your procedure will work if you move past the intake closure. The best way to be sure is to look for the exhaust to close and watch for the intake on the cylinder to just start to open; that is called 'valve overlap'. At that point, the OTHER cylinder in the 'companion' pair is for sure on the base circle of its cam lobes (and will be close to TDC on the compression/combustion cycle of that other cylinder, where the valves are surely well closed).

For example, rotate until #1 exhaust is closing and #1 intake just starts to open; then you know that #1 cylinder is at valve overlap, and you adjust on #6 at that point.