For this article I'll share some techniques I've used to make my panel lines and rivets blend more smoothly into my skin work. In my early skins, you can see that my panel lines are very obvious, and I later wanted to tone this down, but just less opacity didn't look very good in some cases.
Firstly, we'll show a basic panel and rivet set, drawn in pure black and white, using the techniques shown
in other tutorials 
on this site.
Using a simple gray base color, with surface shaders created using techniques in my
surface effects tutorial on this site. Panel lines and rivets in black are way to obvious as you can see.
The most basic solution is to just lower the rivet and line transparency, but this sometimes just looks washed out as shown below. I'll outline some better options.
My favorite method involves making copies of the rivet and panel layers, and manipulating them. Lets take the panel lines. Copy the layer, and invert the color on the copy layer, then move it below the original panel line layer. Now you should have black lines, over white lines. Now by using the "gaussion blur" filter on the white lines layer to blur it and make the edges soft, you should get this effect when the black line layer is hidden:
When you add back in the black line layer and adjust their transparencies to look good, you get this effect. Notice the small white high light rim around each panel line? I personally think this has more depth than just fading the black lines.
Linear Mode
