Hmm . maybe its smart to put some examples.
after some playing i came to this setting
Normal brush with random scratches.tif
Options
brush rotation : 180
Rotation and radius : 100, both in pen mode
Jitter : 0,60
Sharp shape : checked
falloff : 0
So the main problem i have is the softness of the brush . i cant get those hard edges like in PS
thanks again