Plucking birds by hand is a thankless task, if you only have a small number of birds then this is probably your only economic option. However if you have a large quantity of birds or have a number of birds to pluck in a short space of time (plucking turkeys at Christmas) then there are several options.
Wet Plucking: Wet plucking can be as simple as plunging the bird into very hot water (NOT boiling) a number of times and then plucking out the feathers by hand. This gives better results than just plucking by hand. To improve the finish the bird can then be waxed. This involves melting wax in a tank of hot water and immersing the bird. When the bird is removed, the wax solidifies and when removed it peels away any remaining feathers and down. Removing the wax can be done with a plucking machine which typically has rubber fingers on rotating drums. These fingers grip the wax ripping it off the bird. The used wax can be re-melted and sieved to remove the debris and reused. By using this type of wet plucking, you are able to get a very good finish to the bird with all the down removed and the cost of a scalding tank and a wet plucker is considerably less than a dry plucker. It is worth noting that because the bird has been immersed in hot water its shelf life is reduced.
Dry Plucking: Dry plucking involves holding the bird against a set of rotating dishes which come together gripping the feathers and pulling them out. A fan provides suction that channels the feathers away from the discs, usually to a container or sack. If a bird has been hung for a few days (such as pheasant) then this is usually the only option. Wet plucking can work but the skin will have become more delicate and easily torn. Dry pluckers are very noisy and hearing defenders are essential. It may also be a problem if you have neighbours. See an example of a dry plucking machine. The main advantage of a dry plucker is that it is possible to pluck about 50 pheasants in an hour (TIP: removing the tail feathers by hand greatly speeds up the operation). The cost of the machine is fairly high (typically in excess of £1500/$2000) in comparison to wet plucking. Also you need to factor in that there is a lot of moving parts that will wear out and need replacing.
If you do want to buy a dry plucker you have to be realistic with your needs. The plucker shown in the link above is not a full commercial machine and will NOT pluck birds all day like turkeys (for this type of operation you would need something like the Quick 11 Super Fast Dry Plucker). Plucking birds greatly increases the appearance and value and makes them suitable for freezing. You may also want to consider a wrapping machine. Birds wrapped onto polystyrene trays are easier to transport and freeze.
As with all types of produce, if you are considering selling to the public (or giving away to friends) make sure that you know all the relevant legislation. Your local Health Official is always a good place to start. You now just have to decide whether to continue plucking by hand, or make the investment and reduce your workload.