RE:(paintin) Valiant Miniatures

To weather a light coloured miniature use crushed artist pastels
(the dry sort) apply with a soft brush, to panel edges, vents and
exhausts.
An alternative dust can be got from grinding graphite pencils. I use a
piece
of fine wet and dry emery paper to grind the pastels. I use the cheap
ones
made in China.

If you want to allow retouching of the weathering
then seal the base layer first with acrylic varnish. Weather and when
desired effect - seal with layer of acrylic varnish. If you screw up it
can
be rubbed off the sealed base coat with a wet cloth/brush. If you
weather on 
unsealed base coat then its pretty permanent, but can be lightened by
dry
brushing it waya but not very difficult to completely remove. Using a
wet 
cloth/brush makes a mess.

This gives a good grimy used look and can be used in conjunction with
out-lining of recesses with a grey wash.

Another interesting technique is to undercoat in black or grey and then
heavy dry brush in white as the under-coat. If using a light top coat
you
get reasonable gradual shading as the darker under coat creates shadows
and
the dry-brushed highlights reinforce the top coat to make it look
lighter.
This relies on the light top coat being semi-translucent which white and
yellow based colours usually are when brushed.

tim jones