Clear the bank above ground and then go underground

Personally, I recommend carrying both smoke launchers and smoke grenades when on the attacking side. After completing your secondary resupply, you will have five smoke launchers on hand, and as long as you have a medic in the open to hit all the smoke grenades when attacking, you can basically provide very good cover for the entire attacking side. Shooting smoke grenades while rescuing teammates can also and will continue to obscure the opposing machine gunner's suppression.