Washing Technique to detail

Another option that is very popular is a "Sludge Wash." Essentually, it is acrylic paint thinned with water and dish soap. This was a feature article in FSM, specifically; November 2001, page 42, by Paul Boyer tittled, "Quick and Easy Weathering." I believe you can find on this site under Techniques:
http://www.finescale.com/fsm/default.aspx?c=a&id=294
I use this technique all the time for my models and it works great. What I do is similar, only I use Van Gogh artist acrylics:
1. After the model's color coats have been applied and are thoroughly cured, I airbrush a protective coat of Future all over the model.
2. I mix the color(s) I need for the shade of wash for the model
3. I add approx one eye-dropper full of water and mix it with the paint in an empty film canister.
4. I then add 1/2 half eye-dropper of dish soap and slowly stir the mix until well blended. *Note: Depending on how much dish soap you add, the consistancy will be thick or thin. I tend to mix mine on the thin side as a matter of preference.
5. With a soft paintbrush, I paint the wash over details, panel lines, landing gear, etc. The beauty of this technique is that, if you make a mistake, or don't like the color, the wash can be safely and completely removed with a damp napkin or cloth and try again.
6. After the wash has been left to dry for approx. 15 min., I use dampened Q-tips and small folded napkin squares, I wipe off the excess wash from around the selected panels, recesses, etc.
7. When I'm satisfied with how things are looking, I finish by airbrushing a sealing coat of gloss or flat (depending on what your project calls for.)
Give it a shot, you'll get a kick out of how easy it is! Good luck.

Or if using acrylics you can use a wash without worries as they are waterproof once dry and will not ruin the previous coats.

Thanks, I am going to give the water colour method ago

You could always try a water colour wash, as this would give you the same effect without the risk of damage to the base coat.

Karl

Your wash will be applied after your base coat. The wash medium should be neutral as not to affect your base finish. You can use a variety of techniques to acheive this. Do a forum search as this topic has been exhaustively touched upon, or go to Swannysmodels.com for step by step instructions.