This trophy is fairly easy to get.
The mission you want is called 'Numbers'.
When you start off you start with dual pistols but later on in the missions you will find 2 different dual SMGs that you can pick up.
Play it on recruit because it can be a bit tricky sometimes. If you die, you can still get the trophy and you can even accidentally pick up a non dual wield weapon as long as you don't fire it.