Clear the bank above ground and then go underground

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