Finding TDC…

Forgive me if I say anything stupid here...

Trying to find TDC using the coat-hanger-in-the-spark-plug-hole method. Piston comes up, up, up, valves are fully seated, and you're done. But.... The engine is in the car and the exhaust manifolds are installed, therefore I will not be able to see if the valves are seated, right? What am I to do? Thanks.

BTW, where is everybody?
Author: 69 Polara