Hi All!
I restarted building models 3 yrs. ago (after a 10yrs. break), and still trying to make friend with the new techniques...
Using washes, CM, is OK... but I have no luck with the pigments.
I use MIG pigments, and if I create thick mud layer, it's OK to make it touchproof with the AK fixer.
My probelm is that if I just want to create a very light dusty layer, I cannot use the fixer, because it washes the "dust" and it will be kinda "dust after the rain" feeling. Also sometimes the fixer dries with a shiny borderline.
Is it possible to make the light dust layer touchproof somehow?
When I say light dust layer, I mean something You can see in this pic (e.g. the top of the hood):

I apply dust pigment(and really most pigments) with a q-tip dampened in water. Once the pigment has dried, go back over the areas you wish to keep, with a q-tip dampened with IPA. Then, I rub the pigment with a cotton swab. Build up layers of clear flat, at low pressure. And, done.

You can see the effect on the horizontal surfaces.

Thank You! Will try it.
Once I aplied flat clear over pigments (without IPA), but the dust wanished.

I would just airbrush very diluted dust colored enamels and build up the effect, then tweak it with thinner. You can also add some dry pigments for variation when the paint is dry. I would recommend the paints from AK- Interactive

An alternative to using pigments to achieve the effect of an even, but light dust coat is a dust-colored glaze applied by airbrush.

A glaze is transparent, and allows the underlying colors to show through, but will still impart a subtle "dusty" look that can be varied to look heavier or lighter in different areas. It will "tone down" bright colors on markings and tie the overall finish, detail painting and markings together giving a unified appearance.

I usually use Tamiya Buff (XF-57), but not always and not exclusively. I usually try to match the glaze color with the lightest shade of the colors I plan to use on any base. In addition to Buff, I sometimes mix in Khaki, Flat Earth or Deck Tan with the Buff.

I mix my dust glazes to the following approximate ratio - drops = 1:2:17 or percentages = 5% paint, 10% clear gloss, 85% thinners)

Tamiya Buff XF-57:1 part (or what ever paint color mix is used)
Tamiya Clear Gloss X-20:2 parts
Thinners:17 parts

The key to this is the clear gloss which adds binders back into the mixture and helps to apply the pigments smoothly and evenly. The clear gloss can create a slightly egg-shell satin look, but this is easily countered by final flat coats.

The glaze can be built up in layers, heavier on the lower and rear areas (as desired) and lighter on the sides and upper surfaces. I usually test it on the bottom of the hull, and then start by applying an overall coat, followed by a coat or two on just the sides, rear and lower hull, followed by another layer just on the lower hull and rear.

Try this out on the bottom of the model or some other test subject to understand how it works. You really can't see the effect until it dries, so if you spray so much that you can really see it, you've probably added more than you wanted. You can always go back and add another layer or two (or more) to intensify the effect.

The glaze "dust" is as durable as any other paint applied and does not require any "fixers" etc.

Just another option to consider.

Mokush;
I have found that with pastel chalks, found at art supply stores, I can do some really convincing dust. Especially the kind you find in dry arid climate, like the desert. With a hobby knife you just shave the ends a little to create a small pile of fine powder and apply with a soft brush. I do not use fixer and never have a problem with it wearing off. I usually apply more than is needed and remove the excess with a soft sable brush, usually of bigger size. I have even scrubbed away dust with a stiff brush, to get just the right effect. Feel free to send me a pm if you have questions. Cheers.

Gentlemen!
Thank You for the help. I'll try what You've advice!