Is there really is any difference between the weathering powders I have been using for locos and rolling stock for the last year, and standard makeup products - if so, I can't see it.
I've been using a set of Panpowder Pastel brand powders I bought I my LHS for weathering of locos for the last year or so.. They really work well and I like the realistic effects. The set I bought was only greys - twelve shades between chalk white to light gray to dark gray to charcoal black.
Last Sunday, I wanted some reds and browns to weather my trailer park and went on line to find it.
As always when I want something cheap and fast I tried Amazon first. When I searched that site for the Panpowder Pastel product name, it brought up gobs of women's makeup kits at prices about 1/3 to 1/5th that I found found for weathering powders at internet model train stores. So I ordered two sets of women's makeup shades, which, per the usual Amazon efficiency, arrived within two days.
Instead of a dozen two-inch wide tubs of powder cast into the container as in the model train product, there are two dozen one inch wide tubs in the women's makeup set - (same depth) - I know this means there is only about half the total amount of powder, but there is plenty, and a wider selection of shades: my set of powders from light red to dark browns to dark red-brown gives me every possible shade of lightly rusted to ruined! Same Product name and logo, too!
If there is any difference in the material, how you apply it, or how well it works, I can't see it . . . .