Heres how I do it. I approach the target using the map to initially line myself up. I normally calibrate long before I penetrate the enemy dar ring. Once inside the ring I check for enemy fighters, go into bombsight mode, and use the forward command to look ahead in bombsight mode.
When in bombight mode line up your mouse arrow with the middle sight line so you know what center is when looking ahead. You can normally see targets ahead of you at least 10 miles out, farther of they are burning. So now you are in bombsight mode,look forward using zoom, and you see your target ahead of you. Now use the stick to turn the bomber so that bombsight "center" is lined up on target.
From there I normally go into front gunner/F-3 view as I finish my approach. That way I can see incoming threats, and another thing. When in a gunners position, after hitting f-3 view, you can make little adjustments with your rudders without throwing your calibration off.
Ive even circled targets in front gun/F-3 mode, turning with rudders, without a need to recalibrate. Should you actually drop bombs you always need to recalibrate because the weight of the airplane changes.
F-3 views while in gun positions are extremely helpful and useful. Almost all my F-3 view time is from gunner positions.