In Pictures: How to Clean and Retouch Old Photos w...
4. Select the Clone brush from the vertical toolbar and adjust the brush size to suit your work area. This will depend on the size and resolution of your picture. A good tip is to set the Opacity on the Clone brush to 50 per cent as this will have a relatively gentle effect and will make it easier to blend the cloned area to the original.
In Pictures: How to Clean and Retouch Old Photos with Paint Shop Pro