Which pencil is best for watercolor sketching?

While there is no need for more than a small selection, pencils are a valuable part of your "painting" equipment. The photo above shows you a sample of what I use and keep in my art studio.

The most common use of pencils in watercolor painting is to make the initial sketch of the painting and put in the main lines of your subject as a guideline for applying the paint. Detailed drawing and shadings are not necessary, waste time, can damage the paper, and interfere with the paint application.

Although graphite pencils come in a very soft to a very hard range, the more extreme choices are actually less useful: very soft pencils can smear while very hard ones make light marks and can "dig" into the paper and leave dark spots and discoloration when the paint is applied. I usually use an HB or a 2B pencil--both are medium hard graphite pencils.

Watercolor pencils which are water-soluble can be used as well for sketching. However, I prefer to use them when I am doing a quick watercolor painting. These are very good for travel when time and space are limited.

Now for an eraser.....
A kneaded or "putty eraser" is used for removing umwanted marks from watercolor paper. It is extremely soft, absorbs graphite into itself and most important - does not damage the paper. It can be shaped to fit into small areas. If a drawing is going to require much erasures (such as one with perspective, i.e. a street scene) then it is sometimes better to make your original drawing on sketch paper rather than watercolor paper and transfer your drawing to the watercolor paper when complete.