If you are asking about rounding the top and bottom edges of the countertop, use a 1/8" bit for the bottom and 1/4" bit for the top. If you are doing a 3/4" thick piece then you probably will want to use the 1/8" bit for both. Always at least radius the top of whatever you are coating. It lets the resin flow much better over the edge.
Are you leveling or putting a radius on the edges?
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