need help with washes

I'm with Peridixon. Apply the wash where you want it with a small brush. You may have ot repeat the application, but isn't that better than risking a really good paint job and decals?

Here is something I stumbled on by accident, If you are using waterbased paints as you wash after you seal it with clear coat you can add a touch of liquid soap to some clear water then brush or dab the water onto the spot you are working on then wait for it to settle then dab or brush on the thinned wash and it will flow along the same path the water just took . I have tried this with armor and flat coats of clear but I waited until the water had just about completely dried so that only the nooks and crannies soaked up the wash.

I use a faily small flat brush and I apply my wash only around raised and recessed details like bolts and eginge deck covers, not the entire model. to remove the excess this is what i do:
1. Airbrush a glosscoat (I use Future Floor polish)
2.apply wash and wait for it to dry.
3. Use a Q-tip and barely dip it in the proper thinner. Be extra carfeul not to get too much or it will ruin the paint and show the bare plastic. You dont want to soak it, just a Very very very small amount.
4. scrub the areas where you dont want the wash. Sometimes you have to scrub harder than others.
5. spray the flatcoat
6. drybrush raised detail to even more fully show the wash

here is a pic of my latest model using this technique.

I've never really liked the appearance of a cover-all wash, so instead of applying the wash to the entire vehicle and trying to remove the excess, you might try using a very small brush and applying the wash only on the panel lines, around raised detail and the like. This way you have less clean-up to mess with. You might need to use a more concentrated wash to do this. I actually use a drafting pen with a .5mm tip on the panel lines first, then blend it in with the wash over it.