I used Intergrain Exterior UltraClear (Marine Grade and WaterProof and non-yellowing) on my garden bench without issue.

https://www.bunnings.com.au/intergra...inish_p1520102


I've just used a box finished technique called Hard Burnishing on a number of Coasters.
Some of which are End Grain Coasters and the others are Long Grain Coasters.
This technique is supposed to make it waterproof.

But since these are coasters and not boxes I have a query.
Could I use Intergrain Exterior UltraClear (already purchased) on the Coasters instead of Polyurethane ($60?) ?
And would I use the same technique?
i.e. 220 grit sanding | first coat | 400 grit sanding | second coat

Thanks in advance