Paint issues can effect the value of your house, so it is important to determine the quality and finish of the job. Most important is to determine if the surfaces were dusted and cleaned prior to the initial or repainting.
Internally it is recommended that you paint three coats onto fresh plasterboard and preferably with a roller. It is also better to have at least the first coat with a roller while the remaing coast can be with a spray gun.
While externally it is less about the method and more about the quality of the paint used.
All preparation and painting works should be adhered to the A/S 2311:2009 Painting of Buildings standard.