The left or the right one?
Left:
-Basecolour
-Wash with ink or GW wash, be sloppy
- Make a wash with a colour 1 or more shades whiter then the base
- Paint a panel
- Take some cloth and remove paint
- and repeat
Right
-Basecolour
-Wash with ink or GW wash, be sloppy
- Make a wash with a colour 1 or more shades whiter then the base and paint stripes
- Repeat with lighter colour
I both cases I use the drips as a base for my rust technique, the second one is much faster but very easy to get wrong if the paint isn't thinned enough. The first one you just start with very thinned paint, and the longer you leave it on the more pronounced the outline will be. Coincidentally, it is the same method I use for whitewashing vehicles.
Hope that helps.