Thanks, guys...much appreciate the comments!
Rudy- I use a mixture that I concocted with some 'brush cleaner' water with some other additions like a drop of dish soap to break the tension of the water, tamiya flat black, smoke, rubber, flat brown and semi gloss black. It is constantly being added to to top it up, so it is always different! I apply with a Q-Tip, paint brush or rag, depending on what I am dirtying up.