A great starter set of high quality sandpaper perfect for wet and dry finishing.  2 sheets of 400/600/800/1000 grit so 8 shees in total.
 
To use wet and dry sandpaper on your components - start by grabbing a bowl of water and a tea towel, dip your 400 grit in the water and sand around the edges of your component, continue to move through the grits until you reach 1000 this should give you a lovely smooth finish.  If you want to buff your component further you can get finer finishing sandpapers from your local hardware or hobby store.  I personally dont recommend sanding on the top of your component if your using a slab method, just finish the edges and if you like tidy the back (Also totally not necessary)