Best attack angle I've found is to get 1- 1.5k alt advantage, displaced to one side of flght path. Build speed to be a bit faster than target, and get a bit ahead of them.
Then -- and this is the fun part -- roll into the target from the side, ahead, and especially above. You dive towards where he will be and time it so he flies into your sight as you get close. In firing range you should be almost directly above the target swooping almost straight down on the wing root. Blast away, and pull up as you scream to the far side of their flight path...roll to again be flying parallel, but on their opposite side. Build up speed again, rinse, and repeat.
This attack gives them a very short winddow with you in their sights. Most importantly, from their perspective your position, your direction, and your speed are constantly changing -- so they have to continually adjust their lead for their entire firing window. When you get to your closest part, they have to swing their guns a REALLY long way to keep tracking, and you will likely cut through a chunk of their view circle with them having no chance to shoot. If you reach the top of the gunner's upward angle, he has to rotate the turret (slow compared to other movements) and cant just raise the guns to keep tracking. And, when you cross the bombers' path, you get some free time while he turns the guns to catch up to you -- which lets you get farther away.
Next favorite is pure vertical. Get over them by 1-1.5k, get a faster level flight speed, and get ahead. Roll inverted (so you can see), pull down on them, and fire away at the wing roots. Pull up and extend...repeat. Its a little riskier, and a good gunner can rip you up if you pull out at the wrong time. But it is faster, and still very safe since the vertical shot from that top[ gun is one of the very toughest.
But most important is the simple rule -- never, ever, ever hang on a bomber's 6 (especially if you're slow). It's hard to stick to it, but most every time I die to a bomber its because I ignored the principle.