do I clear flat before wash?

You have to be careful if you "wash" on a dull coat. Washes work best on a glossy surface because you can easily remove/manipulate the wash on a glossy surface. If you wash on a flat surface, you might stain the coat and it will be very difficult, to remove unwanted wash from the flat surface.

I would change your order to something like this:

Simple plan:
Paint
Gloss coat
Decals (The gloss prevents silvering)
Gloss coat (seals decals and preps for wash)
Wash
Dull coat (Optional)
Dry-brush
Dull coat (Optional)
Weather
(Final, optional Dull coat to seal, however it will affect pastels used for weathering)

This is the basic outline I use when finishing armor. However, this is just a simple plan and a lot depends on what you're building (A/C, armor, autos, etc), the type of finish you're looking for (factory fresh, slightly weathered, heavily paint-chipped, or trashed), and the specific layering you are looking for. In general, there is no set rule on exacly how to apply these layers, but this is a good starting point (IMHO).

Foster