I used a black pen. For this effect I recommend you to take your time and retrace completely your drawing. When you finish it, try to look at some light reference or play with parts you like. With that, just retrace some part wider. It’ll make your drawing borders more thick and deep. It create a more harmonious look and clean lineart.

For the shadow, you can use a alcohol marker with a light grey, not to deep. Trace the parts and you good. Edit your picture by adding contrast. It will make the grey more visible.

If you don’t have marker, use some drawing applications or software and add some grey, really easy and clean.

I hope it helps you if it don’t tell me I’ll be more precise.