Maybe I didn't understand it right.
But once you know speed and course (aob), it should be as easy as aim with the attack periscope to the ship, place speed&aob in the TDC, and a estimated range (very rought one, by eye) and fire.
I don't see any advantage using this method. In fact it is very uncomfortable if you are targetting multiple ships which are sharing speed&heading
Could someone explain it further? Why is it better than classic method?