once I got the black how I wanted it, I used the same idea to get the silver edges on where the paint had been scrapped away by moving rocks and other debris
I like the odd shape of the sponge because it gives you a couple better angels and edges for getting into tight spots. and if you make a mistake you just flip the sponge and use a wet side with no paint on it to clean up the blending.
And where did a Desert Rat find to place this siege shield? Well on a possessed ghost Vindicator of dewm, of course!
Hope this helps out some fellow 'tread heads' out there with creating uniform effects across long areas.