I did manage to get out into the workshop today as it was, for once, warm enough, which allowed me to do the messy stuff that I'd be a dead man if I tried on the dining table.
I put together a couple more of the Woodland Scenics tree armatures + rubberised horsehair + flock trees, in addition to the willow - I'd have done more, but managed to tweak my back shifting things to make space to set up more trees to dry, so decided to call it a day after two. Not been a good weekend so far.
On the good side, I've now had a lazy afternoon stretched out on the bed watching various YouTube scenery how-to videos!
Anyway - the magic stuff is that mythical substance, Johnson's Klear. It isn't actually available in the UK as Klear at present: it's now called 'Pledge Multi-Surface Wax', but it appears to do the same thing, namely dry to a clear almost-sealant type coat. Big thanks to Matthias Darrow, who pointed out its usefulness to me in the comments on a previous post. It's not that easy to come by (there are rumours Morrison's stock it but I failed to find any), but I managed to score a decently cheap supplier on Amazon.
As you can see, it's messy, and you do need to leave it to dry someplace it's not going to get knocked, etc.