Bombing is difficult but i spend half the time in one. When in historical battles, always have a buddy as fighter flying next to you.
I utitlize several tricks. High altitude carpet bombing on columns for example. But this take practice and skill. Most arcade players wont even bother going above 2 KM.
Another one is to fly high, then when approaching the target, you start to dive, gain imense speed and then dive shallow towards your target (Stuka's divebombed at 90 degrees. If you are not flying a divebomber, Do it in an angle around 40 degrees)
Some bombers have advantages over others.
The A-20G is an excellent light bomber with 6 powerfull .50's in the nose and reasonable defensive armament and armour. Bombing selection is poor however, with only 4 x 500KG bombs.
The B-25J is more manouverable then the A-20G, has lower speed but far better defensive armament and armour. Aswel as a wide selection of bombs
When it comes to actuall bombing the Wellington has the best bombing layout. one gigantic 4000LB bomb. Or how bout 2 torpedo's? No other plane has that in its rank.
Soviet bombers are rather weakish in defensive armament initially and carry little payload. They are manouverable however.
German bombers are pretty cool low tier, later on they suck. But then comes the DO217 E2 wich is epic.