I know I'm probably too late with any suggestions,but let me start by saying DON'T add another coat of Dullcote over your final wash...it's what gives it a 3-dimensional appearance. Once you Dullcote it down it takes it to more of a 2-D appearance.....trust me,I had this experience already with my armor components. By layering the weathering it builds up to give a natural look of age which is what we're after. If you just seal in it all to one base level it will look stagnant and artificial.
Oh,and if I am too late you can always go back in with some very watered down wash to build back up some layers. 
On to topical....the key here is to do it before you start the washes. Again if I'm too late,you can build it back up with a minor wash. Again,the key being to build on the topical scratch's to add an appearance of age.
Steve