I've put together a series of video tutorials covering the basics of my three favorite weathering methods: pencils, oils and pastels. The image below shows the results of all three techniques applied over two different base coats.
The second video in the series demonstrates using small dots of water mixable oil paints to weather a vehicle. This is most commonly referred to as the dot filter method.
It cuts off at the end to stay under the ten minute maximum - and I'll post part two of this video shortly.