I love to bring my curated case of Holbein, Schmincke and Daniel Smith watercolours with me when I travel so that I am "forced" to use them. Now, I love my watercolours but they can be a bit trying and unforgivable when you go in with a heavy hand.
I usually start with a light pencil sketch, removing most of the graphite with a kneaded eraser so that all that is left is a light guideline of my initial sketch. Yep, watercolours do not get along with graphite. Some people do enjoy letting the graphite marks show through their watercoloured pieces though. As for me, I feel that without the obvious line markings, I can still make adjustments to my initial sketch. (You may notice that the completed eye is actually smaller than my initial sketch...because I suck at sketching! *lol*)
Then I go in with a very light wash of colours (watercolours dry much much lighter than when they are wet). Once that layer is dry, I start building up my colours. This is the stage when most people give up because it looks terrible. *winks* The key is to mix your colours on your pan rather than on your paper so you have more control of the colours. And always remove some paint on a paper towel first.
Since I only brought one travel-size brush with me, I finished off the eyelashes with coloured pencils and added white highlights with a gel pen.
P/s: What about you? What art supplies do you bring when you travel?