well, I'd say your best bet would be an airbrush. That's about the only way you could soften the edges outside of some fairly intensive blending or fiddling with oils.

Songing, that I think that requires a good set of vocal cords and years of practice. Sponging, that's pretty simple. Basically dip a piece of sponge in paint and dab it on a towel until the pattern is broken then lightly dap the edges of panels or other places chipping would happen. There's two ways, one is to use a dark brown first and then go back with a brush to hit the center of the chip with boltgun metal and and a white or gray higlight along the bottom edge of the chip. THat way gives a good bit of depth but I think looks odd at epic scale. The other way is just sponge with boltgun and then lightly sponge again with mithril silver.