Alastair, good point. I deliberately avoided "scale effect', partly because it's controversial and partly because if it is a valid concept, it's much less relevant to 1/6th. I'm far from convinced it's a concept of any use to us.
The theory is that you lighten every colour applied. That is to misunderstand how colour works. All that approach can achieve is to change the brightness of the whole vehicle. That fails to take into account hue and saturation, which are the real key to getting a good scale effect. As I've suggested on other threads, all this blah about pre- and post-shading and colour modulation, beloved of plastic modellers, is hype intended to create fashions which the so-called experts can then exploit to make the rest of us feel inadequate (or to sell over-priced and unnecessary weathering materials). I think it's all best avoided, but that's a personal opinion.
I do subscribe to researching and applying as authentic a base coat as possible, without adulteration. I then set about it to do two things, render the detail and apply operational effects. Rendering is just a matter of artificially emphasising the highlights and shadows. In photographic terms, it's about increasing the contrast. You don't do that by only increasing the lighter shades. I suspect what people who advocate "scale effect" are really trying to do is to desaturate the colour, which you don't do by making a colour lighter. That's why I say that 'scale effects" misunderstands how colour works.
I wrote a lot on this on my Cent thread and I have a YouTube video to make about the whole subject of weathering. Here is a screen from my video showing what I mean:
To do that successfully, it's best to use oils, which are translucent and can be built up in layers.
