Well, it really is that simple actually. The main part of shining up paint is how well the vehicle was painted to begin with. You can only produce as much of a shine, or gloss, as the paint will allow. This is why a good paint job costs, using quality materials and good prep work, is essential.
The polish is what removes slight defects in the paint allowing light to reflect off of the paint at a sharper angle instead of at many different angles (think of paint that is swirly that makes the paint look dull).
The "smooth" part is achieved by a combination of a quality paint job (no orange peel) and polishing the paint and removing defects.
Any protection you apply only enhances this shine and gloss further, or gives it a wet look. Applying protection to unpolished paint will never have the same shine or gloss as you can imagine.