I painted this picture in watercolor and then I added pen and ink. I use ultra fine sharpie pens for the pen and ink part. You can use any felt tip marker that is permanent or ink pens.
This Mixed Media is very similar to graphite pencil. It is certainly a little sharper and you can use multiple colors. Or you can use just black or a color of your choice.
When I mix pencil and watercolor I usually do my drawing first. When I mix pen and ink and watercolor I usually do my watercolor painting first. This is a personal choice. You can mix the media in whatever order you like.
When I painted this painting I did not plan on using anything except watercolors. I started by masking out the eggs and some of the twigs in the background. I then layed in my watercolor washes. I loved the way my washes in the background looked but there was not enough value differentiation between the background and the tree limb. (I did like the values of the eggs in the nest.) That is when I decided to add pen and ink to the painting.
I do not always mix media but sometimes it is the perfect way to improve a painting.