Wet sanding will get you as smooth a finish as you will ever need.

Except for the initial scraping with a carbide scraper and sanding with 80 grit to remove any drips - I do all of my sanding wet - it keeps the dust down and the grit of the paper clear. You can easily feel when the paper needs to be replaced.

I prefer 180 grit as the best compromise between material removal and surface finish. 320 to 400 grit used wet will give a real fine finish. Use a plant mister to keep the surface wet and wipe with a wet rag as required.

A polishing compound is typically used on fully cured surfaces as the last thing before a wax. The compound may contaminate the surface of the epoxy and cause bonding problems.