In the end it was a piece of cake, and I've got the look I was trying to go for.
Time to apply some more yellow and the fuselage decals and start the weathering process.
The washable white is surprisingly durable, in that it doesn't lift with tape, but you can wet it and scratch it up a bit with a tooth pick, and obviously giving it a good scrub with water and a brush or cotton bud wears it down naturally.
If you want chipping then you'll need a chipping fluid layer, and if you're doing that then you could just go for any type of white paint.
Anyway, glad to have this bit of the project behind me, even though I made more of a big deal about than it needed to be.
regards.