Since this drawing has a wide range of tones my first step is to ink in the darkest areas as solid black. (click on the image to see a zoomed view)
You must be careful to leave lighter toned areas uninked at this point. If you decide later that you want to make a minor change to an area, it is possible, but not easy or preferred. I will discuss this in a later post.
Here is a closeup of the area under the truck's bumper where the grass overlays the truck shadow.
For most of the darkest inking you can use the largest pen size to speed it up and use finer pens for some of the detail areas. You may need to go over the area several times to get a smooth appearance for the dark shadows.