Welcome Mate!
I'm not a manual targeter myself but the bit you've found is correct, once you move the scope to for example the ship behind the one you just shot at, the aob will automatically be updated by the TDC, speed is of course the same, so you can leave that as is, then all you need to do is re-establish range, this can be guesstimated based on range to the initial target or you can measure it again using the stadimeter, then input it into the TDC open the tube door(s) and fire.
There'll probably be someone along shortly who can answer your question more specifically, or point you to a tutorial.
