Clear the room of all objects such as pieces of furniture. To make sure the paint does not fall on the floor, cover the entire floor with a drop cloth.
Apply joint compound to any cracks in the panelling. Use a trowel for this purpose. Since joint compound shrinks upon drying, you may have to apply two joint compound coats. If that is the case, allow time for the first coat to dry before applying the second coat.
Sand the entire surface you plan to paint with fine-grit sandpaper. Be as thorough as possible because you will have to remove the protective sealant coating from the panelling in order to ensure that the paint sticks properly.
Wipe clean the surface you sanded with a piece of lint-free cloth. Make sure no dust particles remain on the panelling before moving on to the next step.
It is a common practice to install wood panelling in horizontal sections with grooves in between. Fill in all the grooves with joint compound just like you filled the cracks earlier. Sand the freshly applied joint compound if required but let it dry first.
Apply a uniform coat of wood primer with the help of paint brushes, rollers or sprayers. Allow at least two hours for the primer coat to dry. It is a good idea to leave the primer coat on overnight for it to be effective.
Lightly sand the primer coat after it is completely dry. As before, remove dust particles with a lint-free cloth.
It is now time to paint the panelling. For larger sections, use rollers or sprayers. However, for close corners and panelling next to doors and windows, use a brush for painting. Let the first paint coat dry and then apply another one. When the second paint coat dries, check if a third one is required.