I ran across an article that intrigued me last summer, about weathering with watercolour pencils. Embedded in the article was a short video clip wherein the technique is demonstrated.
I really liked the simplicity and effect of this way of doing some subtle shading and weathering so of course off I went to the local art--supply shop and bought a pack of water-colour pencils.
Essentially what you do is dip the pencil in Windex(see post of last Friday, the 26th of Sept.) or water and apply the mark,colour where and how you want…then using a soft damp brush you feather and adjust the colour to the way you want it. There is a bit of a learning curve…but the beauty of the technique is you cannot ruin a model….its water-colour after all….a damp cloth and it's washed off the model….at least until you seal it.
A few months ago I ran across this discussion about water-colour pencils on the Protomodeler website, http://www.protomodeler.com/index.php?/topic/2138-weathering-with-water-soluble-watercolor-pencils/?hl=fading
These guys do some amazing work and it is worth checking out not only the discussion about the water-colours but the whole site. Anyway, the other option discussed was to use the pencils dry, not wetting them before applying the colour. I've tried both methods and for me the dry pencil works better, I seem to have more control of the colour. The important thing is to just give the idea a try…nothing ventured nothing gained!