Ben,

I used Tamiya Spray but the spray was quite wide and unrealistic without using masking tape for the patterns. A good airbrushh would be ideal. I still had to touch up some areas using paint brushes. That initially got me concerned and was also debating on how much weathering I should do. The following is a good reference:

http://www.primeportal.net/the_battlefield.htm

As you can see even the washed and cleansed tanks still showed a lot of weathering, but look at the ones actually in the field!
I hope this helps.