Not very well, because it mainly didn't work. The Schweinfurt Raid is an example when it really didn't work.
The bomber always gets through was a pre-war doctrine that looked good on paper, but didn't work in reality. The British discovered this in the beginning of the war: daylight raids were simply too expensive. Most bombers were (a lot) slower than fighters, less well armed and mostly not armoured.
The Americans thought they could counter it with massive armament, making the bombers virtual flying fortresses that mutually supported each other. They learned pretty soon that was not possible. Not even with the amount of .50 cal in many turrets.
20 mm and 30 mm canons in fighters have a much longer range that .50 machine guns. Fighters are more agile than bombers, and much faster. They could pick a victim, the bombers had to fly on.
Evasion wasn't really possible. Yes, they could manoeuvre, but they had to go to their target and back home again. That's a pretty fixed route - and opened them to fighter attacks. Not to mention AA fire, which was something the Germans (not the Japanese) were pretty good at.
The only way to counter this was to fight a war of attrition: we can shoot down more fighters than you can shoot down bombers. This culminated in the Big Week offensive in Feb 1944, where many of the most experienced pilots of the Luftwaffe on the Western front died.
The other factor was fighter protection. Only when long range fighters (a.o. P-51 Mustang) could accompany the bombers all the way, losses became tolerable.
The same applied to both theatres: daylight precision bombing became practical only when Germany/Japan ran out of well-trained fighter pilots. At the same time, allied fighter aircraft got longer range and their pilots got more experience.
The defensive armament of bombers was only of secondary importance.