what is best product to clean VPI classic platter?

A soft cloth with warm water and a mild dishwasher soap. Not sure if the VPI platter is clear coated, but if it is, stay away from metal polishes with abrasives.
VPI recommends a product formerly known as "Panel Magic" but which is now called "Cabinet Magic", found at Home Depot, Loews, large hardware stores, etc.
I use it myself and find it quite effective on their acrylic platters. Since it works on wood and acrylic it may work on metal as well; you might want to check it out; if it does not damage acrylic I don't see how it could damage metal.