M48A3 Patton

It depends on "where" this Patton is going to be. Me, mine would be in Vietnam. To weather, I would drybrush hatches, handles, edges etc with a silver color to show wear. I have a wash I made of highly diluted black, metal, brown,and rust paint that I would brush over the entire tank. when that drid, I would then get a slightly less diluted wash of reddish-brown to simulate the color of the earth in 'nam and generously do the underside/track areas working my way upward. with less and less. If your tank isn't Vet Nam, simulate a dust or mud color appropriatly. Alot of people like to use chaulks, I never have but the results I've seen usually look great. that is an art by itself

I guess my real question is how to simulate dirt. If you know please let me know. Thanks

jdeltaarrow gives you a pretty good description of how to make a tank worn and dirty.
Are you trying to simulate large clumps of dirt and mud?

I need to know how to paint mud, please.

A good way to get mud on your vehicle is to load up an old toothbrush with paint. You may thin or not, depending on how heavy you want the mud to be. Colors should obviously be earth tones. If you're doing Vietnam, the dirt there was quite red. After loading the brush, pull the bristles back with your fingers and let go. You'll get superb slatter. Try mixing a little Celluclay and dabbing it in the roadwheels to simulate mud; paint it the same color as your toothbrush technique.
Gip Winecoff

Try loading an old toothbrush with paint; thinned or unthinned will be determined by how much mud you want to represent. Obviously choose appropriate earth tones. Tan works real well, unless you're modeling Vietnam mud, which was quite red. After loading the toothbrush, point it at your armor, pull the bristles back and let go! Great splatter! Use this in conjunction with a little Celluclay in the roadwheels and on the tracks, and you shouldn't go wrong.
Gip Winecoff

Thank very much styrene. I will try that tomorrow, because it is to late tonight. But thanks.