I'm not sure I've seen a better streaking effect yet. I still have an Eduard Dr.I that I haven't pushed forward because the streaking thing is something I've been mulling over for a very long time. My initial thought was to try with a rake brush and variously thinned oils (Payne's grey over light blue or linen colour, plus some other contrast streak hue has been the plan). I'll have to look into what you've done here instead, because it's superb.
