Zlov, unfortunately there is no easy answer to this.Some manufacturers confuse the issue by branding polish and wax as the same thing but they're not. Polish will not protect paint and will wash away pretty quickly if not covered by a wax or a sealant.
Also most polish will contain abrasive microbeads to cut into the topcoat therefore increasing shine although this is almost impossible to do by hand. If you want to put a shine on the car and not do any paint rectification then a pure polish (non-abrasive) is what you need (Megs no 7 Glaze is pretty good stuff)
As Chris says the clay is awesome stuff.Run your hand over the bonnet of your cars when clean and if you feel any bumps or slight roughness (or a lot of roughness)then you need to clay it.Very easy to do and you'll be amazed at the difference in the paint quality,even if you can't see the imperfections believe may they are there.
Sorry if this is too long winded
