Thanks,
I like the suggestion of a prior coat of ACF50, allowed to settle and dry a bit. I use ACF50 on my old motorbikes. It's easy to apply, I find the spray a bit thick, so lightly wipe on with a cloth. But it does wash off after a couple of washes and, as you say, I'm pretty sure wouldn't survive long exposure underneath without regular reapplication.
I hadn't thought about applying it first. I will do a small area first, then dry it and check how the UC wax adheres. Nor had I thought about warming the ACF50 up. I will try that, to see if I get improved creep into seams and rivets.
At the moment I'm working through giving the underside a really good clean in readiness. With the cold snap, I'm only managing an hour at a time, even with a fan heater! Just nibbling away at it, but pleased with how clean it's coming up, no corrosion so far, apart from around one of the rear swingarm joints / bushes.
