Greetings fellow captains,
Using TM and manual targeting, I rarely am able to take more than one ship for a givin convoy attack...I'm just not good enough. Occasionally I'll be able to get a fore and stern shot off...but more often than not, I just end up wasting fish. I would recommend, however, if you do want to try to multiple targets, to fire your first salvo on slow speed, and your second on higher speed...that way you can get fairly simultaneous hits and their chances for evasion are less.
Regarding escorts...TM has some wicked destroyers. My old method of lining up at a 90 at periscope depth caused my boat some brutal depth chargings. Now I find I have to go deep, run silent, and slim my profile as much as possible. Of course, this leaves precious little time to collect torpedo data...but oh well! Hope this helps a little.
Good hunting!
Howler