i am not really sure about the washing process
does it raies bolts and nuts and thigs like that or what
if you have a way of washing a tank i would really like to hear how
you do it. I am just a beginer so i am looking to try anything as long
as it dosent use and airbrush

Nick, a wash is basically just really thin paint, actually thinner with just a small amount of paint added. You let it flow into the recesses on the model and it will collect in the low spots and add the illusion of depth. One word of caution: Be careful what you use to thin the paint. If you paint your model with oil based paint for example, and make a wash with laquer thinner, the was will lift your base coat, ruining your paint job. A good rule of thumb is if your base coat is oil, wash with arcylics, if your base coat is arcylic, wash with oils.
Really quick explanation.

Shaun

I found a pretty decent link that expalins some weathering basics.

Weathering Linky