General US-British Summary-
Despite being often derided meta-wise, ground attack can be an expedient means of earning research points and silver lions for upgrading a stock aircraft. While bombs and rockets take precedent, machine guns firing 12.7 AP or greater can effectively destroy targets up to LIGHT PILLBOXES with a couple of passes.
Keep an eye on your surroundings as enemy players will eagerly jump a seemingly easy target. One concern to bear in mind when ground pounding is ammo consumption. What matters more than your total capacity is your AMMO PER GUN. For example, the P-51 has four of its six M2s loaded with 270 rounds and 500 loaded in the other two. As such, you'll be down to TWO GUNS after expending about 1,080 rounds. Being down 66% on your firepower is a severe handicap if you have to defend yourself. Weigh the risk of expending ammunition that you may need in a dogfight.
Ordinance performance varies greatly from weapon to weapon as well as how they are employed, practice your approaches. ASSAULT FUSES on 1000 lb/500 kg bombs will destroy or critically damage your aircraft if you are not bombing from altitude.
The ladder reticle for rocket arc tends to correspond with [Pending]. HVARs are not very precise while RP-3s and Bazookas fly a fairly straight path. Bazooka rockets are effective against LIGHT PILLBOXES but are of little use against TANKS (player or bot) and PILLBOXES.