I find smoke most useful when (either attacking or breaking contact) people remember to deploy smoke and dummy smoke. For example, you are assaulting a flag from south so you get your grenadier to deploy smoke just south of the objective and maybe east or southeast as well. I often see people just smoke in front of them and then charge on through like good old WWI and wonder why they get cut down.

If you deploy concentrated smoke in two avenues of attack it confuses the defenders. I prefer it to just a massive pall of smoke all over the flag which obscures everyones vision and makes it lucky dip time when it gets close up. Cough, cough, can't see, is that friend or foe oh well OPEN FIRE! Sorry man, sorry man!

If you have the smoke in designated areas you can skirt the edges of the smoke as you know the boundaries of the smoke areas as it were. You can emerge from the smoke at a time of your choosing, you then have control over when you have optimum visibility putting you hopefully in a position to shoot first.

In an ideal world I would have a marksman flanking slowly at an elevated angle to provide accurate fire on the defenders, ensuring any fixed gun empacements are neutralized and high priority targets are dealt with, i.e. SAW gunner. In addition a grenadier as a second covering man is always good or SAW gunner depending on preference, squad load out etc.

As a defender I find its often the best when under a smoke assault to simply fall back off the flag to a position where you have clear visibility after getting a few suppressive shots of your own. You then surge back on to the flag just as the smoke on flag clears. Think of it like a tide where your starting point is the flag. Often the attackers are refitting ammo/healing and simply patting themselves on the back, giving it "look at that we are so badass we chased them off the flag, those lily livered chickens". If you can time this right with the clearing of the smoke it is absolutely devastating and hilarious, often they will not have even greyed the flag before you wiped them out.

I've done this a few times on Bi-Ming and similar maps where the assaulters are at an advantage as they can attack from almost 360 degrees of cover. In that situation think of the flag like bait in a kill zone. Why sit rooted to the flag shooting at shadows darting between the trees. Give them a clean run at the flag, get em out in the open. You can control where they will come from to an extent by setting up squads to funnel them on to the flag, most things travel the path of least resistance. You need fire discipline to ensure you get as many opfor into the killzone as possible before you 'start the music' but if you get it to work it's beautiful.