I started sketching with blue lead mechanical pencil and the technique i was using was to turn paper every-time you're sketching from different angle.
I continued to do the same step as last time.
On this one, I kicked off with outlining with black pen for all the shapes. and the technique was the same as the first step. Besides I used a cold grey marker pen to give my shapes shadow.
I did the same thing, and finished it! :)
Here is a closed up to my work, you can see the details.
Black Color pencil
Pencil, the pencil I used was 0.7 with blue lead.
0.3 and 0.8 outline markers
Cold grey or warm grey markers pen