Nige, nice one your T-Bolt is looking great. I would say that it depends why you would, normally, add a wash. If it is simply to help the panel lines stand out and they do without it then I'd say leave well alone. Although you may want to consider washing the panel lines where the large decals are. If you use Turpentine and artist oils then it can always be removed, with a cotton bud dampened in the turps. However if, like me, you apply a wash as part of the weathering and you want your bird weathered then apply a wash. If you use Turps and artist oils and wipe off the surplus in the direction of the wind flow you will get smears from the panel lines which are quite pleasing and they will matt down the finish. That’s the next question to ask yourself, do you want a clean bird? I suspect that you will, because the metal finish looks so good. So the question is clean bird showing off a gorgeous metallic finish, or a weathered one where you might ruin your hard work. I would suggest that you leave it clean, after a couple of coats of Klear and, if you keep the dust off it, you will be able to weather it later, if you desire.
Errrrr.............I hope that makes some sense
Mal