French polishing is a technique for applying shellac. A gauze of similar pad is dampened with shellac. The pad is used to apply a very thin film to your workpiece. Many, many coats are needed to arrive at the completed finish. Each new application partially dissolves the existing finish and blends in.
There are many good books on finishing. My favorites are by Jeff Jewitt, Michael Dresdner, and Bob Flexner.
I can give you the basic of French Polishing, its a lot of work, but you don't find a nicer end finish, maybe more resilant but not nicer.
I don't remember but an issue of Fine Woodworking in the last couple of years has an artical on an easier method of French Polishing. You might want to check the index on their web page and see if you can find it also.
Now tor the lesseon. You need to make a pad. That is a soft cotton cloth an old Tshirt is just the right type of cloth. Cut the cloth into squares about 6 to 8 inches on a side. Then but some cotton batting or cotton puffs about the size of a walnut into the center of a stact of 2 or three layers of the cotten squares. Soak the cotton ball with a 1 lb cut of fress shellac and bring up the sides of the fabric and twist around the ball. The shellac should bleed through the fabric, you don't want it saturated just a light amount of finish that comes through. You then can pound the pad against your other palm to distribute the finish. Keep more shellac in a squeese bottle for refreshing the pad.
The pad then is started on the work piece. You move your hand in a figure 8 motion and bring it into contact with the surface while moving in this pattern, You never let the pad stop moving. just keep making the figure 8's accross the surface to lay down a even coat. Keeping the pad at the right level of mosture is importand and only experience will help here. When you have covered the total surface, you start again at the beginning.. The first coat is hard by the time you have reached the end. The second, third, forth, ..... nth coat all are small build ups on the prior coat. you can't stop the pad or the new shellac will disolve the other layer and you won't have an even finish.
Practice on a scrap of the same wood before you try it on your finished piece.
You will not get lap marks be cause as you pass the pad over the existing surface the new disolves part of the last level. Making the figure 8 also does not let the pad sit in one place long enough to disolve it all. Keep moving quickly and never stop and there will only be a slow build up of the finish.