Superhold hairspray may do the job you require. Any brand, doesn't matter, although I tend to feel you do get what you pay for to a degree so I never buy the really cheap stuff. A good few coats should see you right. Hairspray is essentially a water soluble lacquer. Let each coat dry well. If, when you've finished, the trees display a slight sheen you can get rid of that with a quick, light coat of your favourite matte clear.
Sorry about that side effect. You can get non-perfumed hairspray, apparently. But I've not found any. The smell does go away after awhile. I don't use the stuff other than on the track and usually have to 'borrow' it from His Lordship's bathroom shelf.
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