I did my badly neglected mizzen mast with stuff called Sadolin Clearcoat last October, I think the wood is some kind of pine, was very grey and weathered but sanded up well. Gave it 4 coats, it's an oil/varnish and doesn't flake off, it gradually erodes. It's been through a horrible winter in a salty marine environment and stood up very well. The other thing I noticed is that although I accidently bashed a lump out of the newly applied finish it sort of self-healed and didn't flake off, no water ingress so I am very impressed with it.
Don't know how it would look on ash, anyone tried it on a traveller? <br>