Thanks for the tips guys. Me and my buddy started practising, with one in a spit, flying low and breaking hard as soon as the the other one in the FW starts to get close. It is indeed all about deflection shooting and when you're really close it is blind shooting. If the spit keeps his turn, then you can shoot him without seeing him, because you can (learn to) guess where he will be.
Another thing I learned: if you shoot too soon, you'll ruin your aim and with tracers and stuff you ruin your view as well. It is indeed better to wait until you know which way he will turn, then adjust lead and fire a quick burst. I think this gets better with practise and experience. Right now, on HL I'm just too nervous to actually do that
. Luckily, the FW 190 has immense firepower which makes it easier....