Make a division with 900 OAAB and the rest MRMB. The recommended amount will probably do for WL2. At least 50K I'd think. With this you will attack defenses at either a heli unit or an undefended target somewhere farther than 35 mi from any ground units. At some point no helis will respond meaning they are gone.
Next you got to figure out if there are any ground units within 35 mi. This last time, I just attacked with 1 weapon each and checked the report to see if any ground units responded. If they do you need to just attack an undefended target or another heli unit farther away from the ground unit. It may also be that there are no ground units at WL2, I can't remember.
If your just working the WLs to get GC I'd just avoid the C3s where those offensive bases are close together. That will ensure it's easier. Because you cannot destroy the air units without attacking them directly. They typically don't get resupplied w
Is this still the method? and what unit would those be?
It's a division that you make custom.