I usually guess it visually and fire a spread, which is probably how they did it for real most of the time, hence they didn't get the kind of kills you get in SH with all the assistance on.
But... If I have time, I remain stationary, take a bearing and range estimate and mark it on the map, then wait a minute or two and do it again and mark that on the map too. With two marked points on the map, you can draw a line between them and you've got the target's course, and when you have that, you can draw the angle on bow with a protractor on the map.
Of course what usually happens is they then zig zag, so I go back to firing a spread :rotfl:
Chock