Heres some ways I bomb fields and towns.
Remember its best to use ord on town first as those buildings stay down longest.
I use B24s with 8 1000lb bombs usually, although smaller bombs will get the job done. The green lines are direction of attack. It doesnt show exiting the area and turning around, but you should get the idea. The small target is the aimpoint for your drop. Each "target" represents the release of 1 bomb.
Aim for points on the target that will spread out the most damage, making the most of your blast radius.

Most of the town will be down after your first pass. You will have 2 bombs left to destroy remaining buildings if needed. If others are left when you are empty, call them out and have friendly fighters finish them for you. Or go in low and use your MGs to finish them off.
If the base is giving your team a hard time, and the C47 is in the area to capture, go after the Fighter Hangers. The following pics show small, medium and large airfields.



For Vehicle bases its best to try to capture it intact without wrecking the VHs. All you need to do is kill the 3 AA guns ( 1 manned, the other 2 are AI.)
But if you need to kill the VH aim at the point shown. For V bases I normally take 2000lb bombs and drop just 1 at the area shown. If you are using 1000lb bombs, drop 2 at this point. Ive found its more reliable.

For ports, again all thats needed is the AA to be killed, but as you can see theres alot of it. If you need to kill the VH because its spawning alot of enemy GVs, drop 2 bombs on the aimpoint. Use the rest for what AA guns you can get.

As you can see many of the aimpoints are not directly on top of the target. This is because your drone wingman also drop 1 bomb when you do. Theirs will hit to the left and right of yours, and slightly behind. It should concentrate all the explosive force in one small area, directly on the target.
Try it out and see if it helps you.