Sighting a scope is as easy as how much time and effort you wish to spend taking benched up shots at various ranges. When you start seeing a trajectory then you have made excellent progress.

I wonder how many unzeroed @100 yard scopes are put on rifles that would shoot better with the factory sights. Then I think about the guys at the range who shoot AR-15s and AK-47s benched up on the the 25 yard target and never move to a farther target. (A lot of people spend money on overkill things they do not use to their full potential and would be better with something simpler.)