[Umfuld]

Hey headcase. Welcome.

I don't know of any way to plot on the attack map. But I'm not sure why you need to. Other than seeing the projected path of your torpedo there is no real difference, right?
The only time I use the attack map is to get an idea of what my torps' spread distance will be at point of impact.

Keep using contact updates until you get the hang of it then shut them off if you want to. No one will think any less of you. :p

What I do is mark the target's position a couple of times on the Nav Map as best I can.
If on the suface and within visual range, this is pretty easy. Ask the watch for nearest visual contact and he'll tell you the bearing and range. Just mark that spot on the map. Do it again a minute or two later. Then draw a line with the ruler from the first mark thru the second and on in that direction.
You'll have that ships exact course to plot an intercept.

Same with sound updates if you're under water. Though you won't have exact distance, you should be able to get a rough estimate of their course.