Order of Battle for Weathering?

Welcome wargamer. I'm not sure what you are painting with, but I'm gonna assume acrylics since you call yourself "wargamer". In that case, I would do everything you can in acrylics, then move to enamels/oils, then pigments.

1. Once you've painted your model, I would go ahead and put a satin/gloss coat on it (like Future or a Vallejo varnish).
2. Add decals
3. Add paint chipping with acrylics (or any acrylic techniques before moving on).
4. Add satin/gloss coat (satin works best for washes/streaks)
5. Add a filter if you wish. If not, then add a wash. Enamel washes from AK Interactive are great. Otherwise, you can mix oils and odorless thinners.
6. At this point, the enamel/oil weathering can be remixed by reactivating them with thinners. If you are satisfied, add a satin coat.
7. Now you can add streaking or color modulation with oils. This is basically creating fading or streaks by adding un-thinned or just barely thinned enamels or oils. You can blend it as needed. If lighter shades are used and accidentally creep into panel lines, you may need to redo the wash in some areas.
8. If you are satisfied, I'd add a flat coat and move onto pigments.
9. Pigments sit best on a flat coat. You can brush them on, rub them on with your fingers, or create dust/dirt washes by adding water or any type of thinner. Once they dry, you can wipe them completely off since there is no binder in the mix. You can add white glue to pigments to make mud. I've also coated something with Future and dropped pigments onto it to create rust.
10. You can apply a pigment fixer, but don't add a flat coat, as just about any top coat/varnish will change the shade of the pigments (usually making them darker). Even the pigment fixer makes them slightly darker. Of course, if you want shiny mud, then add some Future or gloss coat. Add a satin coat to pigment mud to create a semi-dried mud look. Or add some dark oil/enamels to make grease over the mud.

I'm not getting into everything that you can do with pigments (or with any weathering). There are many helpful websites and books. I have a semi-complete listing of techniques at my website, but it's not an authority. If you like enamel products for weathering, I would highly recommend Mig Jimenez's new FAQ 2 book. It's pricey, but it's the best authority on modern weathering techniques I've seen.

Hope this helps.

My philosophy is to do weathering last.  After all, that is the case with the prototype.  All the paint and markings were there before it is left outside to weather, so all the weathering is sort of on top of the factory finish.  Using the "salt" method to make paint chips would be something else.  Ordinarily I chip paint with a toothpick and aluminum paint, so I do that after everything else, too.

Don brought up a good point. Usually, I don't plan ahead for my weathering, but if you're doing salt or hairspray chipping, you have to plan out the paint job before hand.

Hey guys,  thanks for all the great tips. I was a little vague in what i was was building,  It a tamiya 1/35 scale german panzerkampwagen III Ausf.n I'm painting it in the dark german grey. Its my first attempt to do any weathering at all.

Thanks.

Keith.