Touch up putty, followed by a coat of primer then 2 coats of paint application, provided walls are in good condition without any cracks or water seepage. If cracks are there we have to apply crack filer in the beginning of the process.
Priming can be skipped if matte finish paint is used. It is always advisable to have an undercoat of primer if a gloss (sheen) finish is desired or when painting a shade way lighter or darker than existing. However, priming does not cost must and it increases the durability of paint, it is advisable to have one.