adjust the exhaust valve just as the intake valve begins to close.
Taken literally, this is anything after the intake centerline, or 110° ATDC. Yes, the exhaust valve is closed.
The link above says to wait until the intake valve is almost closed.
This will always be ABDC. Again, the exhaust valve is closed.
If you don't have a good mental picture of the combustion cycle these methods are not helpful.
At TDC on ignition, both valve are always closed on every engine.
At TDC on overlap, both valve are always open on every engine (except those with extremely mild cam timing such as pre-war).
