It's difficult, and tricky. You cannot ever plot all the contacts of a convoy, and even if you focus on one or two targets, you cannot plot with 100% accuracy. Imagine if you are the skipper of a U-boat, at periscope depth, getting short, 15 second glimpses of the surface. The way I do it, when I first make visual contact, I get a general bearing and range, then drop the scope, and plot them manually on the chart. When I get another bearing and range, another plot. After 4 ~6 plots, I have a pretty good idea where the targets are, where they are headed, and their spatial relationship to my sub. I use this info the make course changes to intercept. Then as I get into 3000m range I focus on getting a solution for shooting. Do I misjudge and get out of position, and lose shooting opportunities? Frequently. That's part of the game, for me.
Do I want or need to see every ship plotted and updated in real time? No. Even with a full crew to aid a captain in real life, I don't think there was someone calling off the info on 20 ships and someone else drawing little squares and updating every 5 seconds
