I've never used Vallejo's washes but have used their paints. Was the wash applied over a glosscoat by chance? If so, you could try a little bit of windex on a small paintbrush or damp (not soaking wet) cloth to try and wipe off the excess. A word of caution here, I routinely use windex to clean up future, so if Future was your glosscoat of choice, too much might damage the glosscoat itself.
If the wash was applied to a flat coat of paint with no glosscoat (or gloss paint) then you might have a problem. Without a glosscoat or gloss paint, the wash would have a tendency to act as a fliter on the areas outisde of the panel lines. Even with carefully trying to clean up around the panel lines, you may end up with a "stained" look similar to what you might see in a drop ceiling tile.