This mission always begins with the teal tank directly opposite you firing at you. So I typically move up immediately. I would stop momentarily just before crossing the upper barricade, and fan out all five rounds of shells from the upper barricade to the lower one, then move up above the upper baricade for protection. Those five rounds will typically take out at least one of the tanks, three if you’re lucky.
For any remaining teal tanks, just apply the usual tactic for teal tanks.
In the process, watch out for rebounding shells from the innocent-looking grey tanks. Due the wide gap between the barricades and the surrounding side walls, shells can rebound at a steep angle and reach you deep behind the barricades. This happened at right about the middle of the above video. Luckily, I was well on my way to the other end of the barricade.