Technical How to make my wooden dash shiny?

I think your best information will come from wooden boat builders. They know the effects of sun and water on the finishes they use. The finishes I use on furniture are not anything I'd recommend for outdoor use.

 

Can’t beat a Hand Rubbed finish.

https://www.highlandwoodworking.com/handrubbedwoodfinish.aspx

 

I sealed my cherry bed wood in 2005 using PPG automotive clear coat.
I cut and buffed it just like the body paint. It's held up extremely well.
I built a bed cover in 2015, but the bed wood was exposed to sun for ten years.