First off welcome to the forums
As to your question what I do is to find seperate solutions for the two ships and determine their distances vs run time for the torpedoes. Usually pretty simple as they are on the same course, same aob, same speed, only variable is the bearing.
I then fire at the furthest target first, giving me time to plug in the solution for the second target and try to calculate its release time so that they both reach their targets at the same time. Sometimes Ill set the first torpedo aimed at the furthest on slow and the second on fast, this gives me ample time to pull it all together and get that gratifying boom boom within a few seconds of one another.
The catch is that if they spot the steamwake it will spoil both solutions. The closer the better
