I heard the word mentioned and was wondering what is a "wash" and how do you perfom one...

Will regular testors paint work?
Do you use a spray bottle?

Maby this is why my models cant get weathered right

I also got these paints...

*runs to garage.....runs back*

"acrylic Paint Concentrate"
Colors: Raw Sienna
Hooker Green
Burnt Sienna
Yellow Oxide
Burnt Umber
Payne's Gray

I got them awhile back when I was into Model trains...they say use lots of water with them.
Could they be the key to realy cool weathering ?

What I do is mix paint and thinner in a ratio of about 90% thinner to 10% paint. Make sure you test this mixture on an old model first. After I get it to my liking, I paint it into recesses and panel lines so as to accent them and make them look deeper. You will probably have to do several layers to get the desired effect.

As for your paints, I personally don't use acrylics, but some folks do. I prefer artist oils because for me, I have a better flow.

Another thing, if when ading this mix to your panel lines and other recesses you go 'outside the lines,' have a Q-Tip (Cotton Bud) with a little bit of thinner on it to clean these up.

There are two kinds of washes - Overall and Local. The overall you take a big'ol brush and cover the AFV. Then you take a clean dry rag and blot the excess off the big open panels leaving the wash in the recesses. Some people don't blot - it's a personal choice.
The local deal (the I use most often) uses a thin brush and like GH said you brush it into crevaces and nooks and cranies corners etc. to accentuate the shodows and lines.
The thinness of the wash helps with capilary action. Cap.action is where the surface tension pulls the wash into and along the panels lines and crevaces. To help with cap. action you can give your AFV a Gloss Coat after you get the basecoat down. You do your washing and decaling on the gloss coat and then you go back and cover it all with another layer of dull coat.
The gloss coat is pretty important for decals (keeps them from silvering) it's kinda optional for the wash. If you're up to it try it. If you want to experiment leave it out. I've done both and can get both to work well. Without the gloss you may have to add a few more wash strokes to get the whole area covered.
There are lots of threads on washes so by all means do a forum search on washes. You'llget a bunch more.

Happy washing!