For the oil streaks ,oil paint heavily thinned , with a brush cut down to 2-3 hairs.Drag it back one streak at a time. Also consider real used oil for this(not kidding).These stains could also be blown back with carefull air brush handeling. The gunfire streaks shown are more than likely pastels.Pastels are good as you can remove them and start again.They may need sealing although this will diminish thier 'look'.
References show drain holes in the engine cowls of a D-9 these will need to be addressed as well.Drain holes ,shell ports , gun powder staining ,oil stain , coolant stain ,exhaust stain, etc!
A list of the streaks marks etc would help to make sure all the bases are covered. Use a different technique for each detail and a really good finish will appear slowly before your eyes, one of the best parts of this for me.Layering is the key to great weathering.
K.H.'s D-9 there is superb in detail ,but missing the throttle linkage ,I just did mine so I noticed immediately. If there is a link showing the scale of that model I would like to see it.