How to use resin so it has an opaque smooth finish and technique involved to make and apply.?

well it depends what colour you use, resin is a clear material, and one can use opaque or translucent pigment to colour it, when it is set, sand any rough areas on wet sandpaper don't use dry as it has toxic dust, when as smooth as possible use a polishing wheel with specialist polish, that's all the info i can give you at the moment if you need more let me know