Everything is done digitally from base drawing to the final coloring.
Here is the process:
First, I draw directly on computer using Wacom Tablet.
I use a thick black line pen I created my own.
Then I change the color line using Photoshop channel mask.
After changing color line to brown in this case, I start coloring around the line.
Here is the base colored image.
Then I place different texture or change the image through filter depending on how I want my final image to appear.
I create this textire separately and past into my image.
And this is the finished image.