How to make a shaded bubble glasses for a storm trooper helmet. I did it for my 3D printed helmet http://www.thingiverse.com/make:244854#comment-1161387

Step 1: Materials and Tools

A plastic bottle with similar shape
Scissors
Sharpie
Knife (actually any knife with a sharp tip)
Some pigmented laquer spray
Cotton sponge
A helmet

Step 2: Cutting Out the Workpiece From the Bottle

Take a bottle and cut a rim and cut it in two. You can make a hole with a knife and proceed with scissors, or make the whole cut with the knife. When cutting in half - follow the bottle seam, don't make the mistake I did (you'll see it in following steps).

Step 3: Cutting the Glasses

Put the "glass" on its place, try to rotate it and find the best position, it should fit the eye rim as close as possible. Then take the sharpie and draw the future cut line along the eye rim. After that take the scissors and cut the workpiece as you see on the photo - actual cut line should be about 1 cm (0.4 in) away from the one, drawn by sharpie - this extra space is needed for putting glue on it.

Now we need to create a "flange", where the glasses would be glued to the helmet. Take the scissors and make perpendicular cuts along the whole workpiece (see last 2 pictures of this step), about 5 mm (0.2 in) from each other. Then unbend the cut pieces forward.

Step 4: Painting

It's important to clear the surface before painting, as during previous steps we were touching the plastic all the time. Take some vodka (we're seeing some Ukrainian one on the photo :) ), moisten the sponge and swipe the glasses from both sides. After that take you have to find a painting place, I took a sheet of craft paper and fixated glasses with plasticine, but you can fixate it with a glue gun.

As you see I found an acrylic tint spray, mine particularly is supposed to be used for tinting the car lights, so just google around for "tint spray".

Unfortunately I don't have pictures of the painting process, but it's pretty straight forward - put a layer, let it dry, but another layer, do so, until you get the tone you want. It took me 6-8 layers to get the tone I wanted.