British mortars (2inch) use your smoke first, I use them as spotting rounds for the FO. Like a flare which are not modelled in the game and radio communications were still in its infancy. Also if you use the few HE first I thinks once they run out you can't use your smoke rounds. US 60 mm direct fire is my first option. The same for 3 Inch British CW and 81 mm Germans. I found for me these tactics work well.