This is for my personal reference. Tutorials are not created by me but by those who created it. For the most part you need a tablet to accomplish this task.Visit wacom.com for more.

wacom tips wrote:

Step 1:
Using Adobe Illustrator and our Wacom pen tablet, we decided to draw a fish.


Step 2:
We clicked on the Paintbrush icon and de-selected all three available options.


Step 3:
We chose a Round brush from the Brushes palette and sketched a goldfish.


Step 4:
Then we added color by moving the fin lines to a top layer and added a different layer for the fin color between the fins and the rest of the fish.


Step 5:
We selected the Brushes palette and increased the size of our brush. We highlighted the Pressure setting for diameter and selected the Angle setting for Calligraphy. Then we flattened our brush and set the pen Angle for Tilt.


Step 6:
We added another layer at the bottom of the fish for body color. We selected the color orange and painted using our large brush, pressing lightly when we needed to squeeze color into the tight areas.


Step 7:
To complete this image, we added highlights and shadows to the fish and filled in the eye.