Hi Sowiet, i am dedicated FW190D9 driver, and so scissors and barrel rolls are esential for em (speed even more

).
Scissors: u fly break turns to the left and right, timed in this way, that the guy behind u flies more or less a straight line. This will normally cause him to overshoot cause he flies a shorter way than u.
To time the reversals right, u must be capable of flying with view back.
My general rule to scissors is the following.
Say i start with a turn left, than when i see the guy rolling left and start to pull left, i quickly roll to the right ad turn right, if the guys wing drops to match my turn, i reverse again. And so on.
Problem in FW190 is that it has very bad low speed handling, try to keep it in scissors over 200mph IAS. Most plane wil handle better, if the guy behind u is smart he waits till u get slow and then will us his superior slow speed handling. In D9 i use scissors only as last resort, my defense with a D9 is most of the time speed. dont always perform the rolls the same way, if i.e. in right turn, u can also quickly roll right instead of left to change direction.
Barrel Roll, functions well against an nme closing fast. Again u try to travel a longer way than him, so he will overshoot(hopefully). Also works well to throw off the aim of guys sitting very close and without a speed advantage, but than again its a last resort move.
The best defense in FW is, from my experience SA. Dont let urself get into situations were u must rely on scissors or barrel rolls. Cause nearly every othr plane if not every other plane is better at the low speed game than u.
Best fly together with a wingman or two, so they can interfer in emergency.