Basically it is the same process as putting a nice finish on a piece of wood.
Sand (usually lengthwise) with progressively finer grit until you get the finish you want. You will have to sand out all the marks from the coarser grit before you move to a still finer grit.
As with wood, the grit you start with is determined by the current surface finish.
The finishing grit is determined by the finish you want. Most hand finished satin blades are from 300 to 600 grit, although some do go as far as 1200--but that is getting real close to polished.
When you get to the finishing grit you must rub only in one direction and not stop while on the blade. Use fresh paper--'wet and dry' or crocus cloth usually.
Be careful not round sharp corners (if there are any).
BE PATIENT AND TAKE IT EASY!
Greg