With your first question I would:
Primer => enamel main coat => black wash => acrylic flat coat
Reason: The wash may have gloss streaks or the the added enamel thinner may scuff the dull coat. It is safer to use the acrylic top coat last...
Windex is fantastic for cleaning out the air brush but spray a cup full of metho just to get any added soap scuds or left over paint out of it. Make sure to pull it apart every now and then for a good deep clean out...
Personal experience always tells me to use hobby branded primer. If you have an air brush it is much cheaper to buy it in liquid form then can like Mr. Surface or Tamiya. But some have had success using automotive primer out of a can o the cheap.
I'll leave the weathering side of things to labstoys but feel free to check out my kits which are normally weathered...
well i need to spray the acrylic clear coat before i do the enamel black wash right?
and whats metho exactly?
and i dont use tamiya acrylics... i use testors enamel, :/ i was debating whether or not to switch to acrylics cause everybody is doing it but im clueless when it comes to cleaning acrylic out of ur gun... plus i have a LOT of industial bottles of enamel thinner lying around... o and mr. hobby isnt really around here in Oregon, USA. and i just get my stuff at hobbytown USA...
Hi Sira, hmmm... my questin is what battle damage ur goin to do first? do you need to do ur kit some scratch effect using paint or really need to damage your kit, then do paint? you can check it out how it looks like my gundam exia, i really do damage my kits, kind of it hurt.... then just using water base paint to do the effect or use tamiya pastel wearthering can also use it.... 
well i want to enamel primer the joints than paint them grey and dry brush them with silver... just really roughly... (does this sound about right to u?) and primer and paint the body black and maybe add some scratches etc. but dont know if i should damage it first or paint it first... than how to color it without leaving brush marks... and maybe touch some edges with silver etc. does this sound right?
