Which clear coat for external door, over colour and raw timber.

G'day all
I eagerly seek some urgent advice.

I am currently restoring a hand-made solid timber pivot door for a customer.
This door is a piece of art. Multiple species, shapes and timber colours,
with the main body of the door sand blasted, colour filled, rubbed back to reveal high spots, then clear coated.
Attachment 464488

The outside poly (?) clear coat was seriously affected by the elements.
Attachment 464490

I have stripped all clear coat (mulitple times), and next is working on refill colour, sand back back, clear coat. Refer photo.
Attachment 464491

My concern is, I cannot find a high-fill, or quick dry enamel blue. I need it to dry, so I can sand it back, then clear coat.

I have used a nitro-cellulose black for the centre panel, and I am about to rub it back and test the Cabots turps-based Marine poly over this.
Attachment 464492

I have a standard oil based blue to try, but it will be 2 days before I can sand it.

My other concern is, will I encounter problems with the Cabots clear single pack poly over the NC black?

Any assistance or advice is appreciated.

Thanks

Graham

I have used Sikkens Cetol HLSE with success on the front door of our house which is fully exposed to the sun during afternoons. The product is used on outdoor furniture and, apparently, on shingle roofs. It also has anti-fungal properties. Sikkens has a wide range of wood "coating/finishing" products and supply good technical information.

Cheers Yvan

Thanks Yvan

My concern is that the Sikkens products are all coloured. I know that the pigments help UV protect the timber, but I am constrained by the original door design.
Also, I don't know how they will react as a top coat over oil-based or NC coloured timber.

I really need an uncoloured clearcoat.

Thanks anyway. :)