These are some of the shading techniques that I use with Sharpies. I'll show you how to do the contour shading and a different technique not shown.
I'm shading 3 basic shapes starting with the heart and cube.
Now I'm finishing up with the cube and sphere.
If you want a more cartoon look to your drawing, this is how you would shade. All you have to do is draw a few abstract shapes where the "light" isn't hitting and color them in w/ a darker shade.
I don't know if you can see the black highlight within the blue shading, but it's good to combine colors while shading.
I put in a bonus guide on how to draw Spongebob Squarepants. I started w the basics... Eyes, nose, mouth.
Then I drew small circles for his holes and shaded his eyes, nose and mouth.
Thanks for watching!!!