You really need some special tools for your purposes. To answer your basic question: there is a tool that threads into the side of the injection pump that freezes the pump shaft. The tool might be inexpensive I'll look if anyone is interested.
By freezing the shaft and removing while the engine is at TDC (really doesn't matter where as long as you don't turn it - but TDC has all the marks lined up also) one can reinstall and go (usually).
We use Bosch's high pressure timing method and it requires a major special tool. Once in with basic timing we also use an inductive piezio transducer style standard timing light for overall testing.
Bosch Master, ASE Master, L1
33 years MB technician