Why are you doing the two hardest Class Missions for Co-Op in Co-Op? Why not do the Cruiser mission which is just "shoot stuff a lot" and the CV Mission? If you don't have good mechanics in CVs, this is certainly an easy way to practice your bombing runs. Once you learn how to drop a target, you should average 10-40k damage per match and finish the grind fairly quickly. The Base XP requires like 80-120 matches anyway, so you've got a fair amount of time on your hands.
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If you do not have CVs and are not interested in playing them, I'd recommend that you take a Battleship with the Slot 4 Propulsion upgrade and a Spotter Plane.
Using the Spotter plane, you can turn it on before you see any bots and fire off a round or two. Bots often fire at the first thing they see, so you can forcibly spot yourself and receive incoming fire as early as possible from as many targets as possible.
Go full speed forward from battle ...
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