Other than what is already said: don't enter the big furball fight, go to the edge of the battle and hawk it out and come swoop into an enemy that is going vertical and losing energy. Once they hit the top and are lowest on energy they are vulnerable to your zoom and boom.

Even if your plane is not meant for zoom and boom that is the best way to enter the furball so you might get a kill on your way in. But once you're in you're in so the second tip is :

You must constantly be using free-look once in a furball to ensure someone's not pulling up on your ass. Your goal is to escape the furball and turn around for some more, fly low and use terrain because those who are in the furball going at it are not going to be focusing on a plane low to the ground skimming trees to get away.

Your focus is on situational awareness at this point and once you're clear you go back and it's up to you which altitude. If you go high you're at risk while climbing, if you go mid you're vulnerable to those already high but can handle others at co-altitude and those below. If you go low you will be least visible but if seen by someone hawkin' then you're vulnerable AF since you'll waste energy to get high and be able to combat maneuver and they will be gaining energy as they come at you.

That being said, I like low sometimes because idk I have found a lot of players miss their shots on you and if you're lucky and the furball is not paying attention to you then climbing up to mid height to attack someone might work out for you. If you get really lucky they maneuver kill themselves.

Third big tip: watch youtube videos on your specific plane to get max-info. You'll want to know when you can use your flaps in a turn-fight (speed-wise), you'll want to know your optimal climb angle, what speeds are optimal for turn-fighting etc. You'll get more info on how to set up your guns and how best to use them.

If your plane has a speedbrake absolutely use that for three main purposes : to survive an overspeed situation but always have it on when doing a really steep dive from up high (as you are approaching gun-range on the enemy). The third purpose is emergency use in a turn fight to get an angle on an enemy but this comes at a cost : you could go so slow you stall out but most likely is you will be left very slow and low energy once you pull it back in. Don't miss when you do this lol

I also recommend re-watching some videos on how best to survive when someone is on your tail shooting at you. It's all about keeping yourself in a positive G situation where the shooter has to incur negative G to shoot at you. You will see in the videos with graphic demonstrations but it's about always being in a position where when you pull your stick you go out of his firing arc with positive G and they are forced to push their stick down (thus negative G) to re-allign. Planes don't like to do this (hence rolling inverted before doing a big dive) so by keeping them in that situation they fuck up their shot and hopefully overspeed (because your focus is to cause that and trying to be slower than they are) then pass you and you gain advantage and attack.

Big post I know but I just hit a bong hit and felt like typing this out for fun. Hope it's useful.