Ahmose, you have use RDUnits, and place a network of Air Fields within range of wherever you want to attack. This could be used to drop air forces. Then you can paint.
I do confirm that before the war level changes that you could in fact take any c3 w/o painting using your navy. At level 3 I don't think it possible anymore. Especially with your navy it is kinda painstaking and dupid.