Oh dear. Sorry to hear that Peder.
You might be able to rescue it by giving the whole thing a good brush with neat white spirit.
I am a bit of a novice at the whole AFV thing - it's been 30+ years since my days with Tamiya kits! But the technique I've been using is 'pin washing' (I think that's what they call it). In other words, rather than washing the whole painted model in a diluted wash (which tends to make the whole thing go muddy), you actually only pin-wash the details you want to pick out - hatches, doors, rivets, raised detailing, etc. The open areas of armour plate / bodywork, you pretty much leave alone.
The way I've been doing it is to liberally apply neat white spirit across a whole area; let it start to evaporate for a few moments so that it's only concentrated around the raised details and in recesses, then using a fine point brush, just touch in a very thinned oil paint wash in your chosen colour into the areas of detail.
Burnt umber works well. For my desert vehicles I've been using a mix of burnt umber and burnt sienna. But really, it needs just a really tiny amount of oil paint in quite a lot of white spirit. Like 1:20 ratio.
If some of the wash escapes from where you want it to go, then using the tip of your fine point brush, just wash it away with neat white spirit, and coax the wash back to where it belongs.
The other thing I've learnt the hard way is that it's better to build up the desired effect slowly in two or three washes, rather than hit it too hard on the first go.
It is, undoubtedly, a painstaking process
But once you've mastered the technique, strangely satisfying