It is a fine looking vehicle Hamish.
Post blasting normally put on a coat of primer to stop the steel gingering. But what primer depends on the final coating.
And if they are going for refurbishment, even if the primer doesn't get damaged by tools, then presumably there will be oil involved, which would be an issue with primer which is slightly porous.
WD40 is a bit light. I would suggest a light oil instead.
I am assuming that whoever does the overhaul will do the painting so will need to do a full degrease anyway before the final painting.
Love those safety three button T shirts and flared jeans on the marshals. And your dad's sports jacket and tie. Those were the days