Hi there
When it comes to painting the outside, things you should make sure of......the surface is sound and dry. If there is any sign of mould or similar wash it down with bleach. This will kill the spores. If the surface is new it may pay for you to seal it with a sealant. They come both as a water or silican base, but the water base is cheaper and easier to use.
For the paint use a good quality paint, that repels water and is breathable. A good paint that contains quartz will give a good even finish along with it being brilliant white.
These are the things my husband does here, time served painter of over 25 years.
In italy you have to be careful about painters. Proffesional italian painters can charge upto 300e a day, where as the cheaper 50e a day are just odd men, that don't understand paint, and will water it down so it is more of a colour wash.
hope this helps, if you want some help drop me a mail at
miccapup@tiscali.co.uk
gill