Using watercolors and pen and ink together is a recipe for success.
Regardless if you choose to lay down the watercolors first and then come in and add details, or sketch your drawing and then add splashes of watercolor, the results are always very endearing, I think. The mediums compliment each other beautifully. The starkness of the ink lines and the looseness and expressive quality of the brush strokes are a marriage made in heaven if you ask me :)
Jamie, of inksnthings is an Illustrator sketching the everyday, everyday :)
If you love this technique, you'll find her work worth following and sharing.
*edited to add - Recently, Ohn Mar Win, an Illustrator surface designer teacher just published a great online class on the subject. You'll enjoy her lovely style, the step by step demonstrations and easy to follow instructions. The class is available on Skillshare (an online resource I absolutely love and have used again and again to learn new skills over the last few years) and is called Sketchbook Practice : Create Freely with Ink and Watercolor.