You will get more control from an airbrush. Some metalizers are specifically made for airbrushing. They are thinned to the proper consistency, something that is very important for airbrushing, especially a metal finish.
Without know what you are painting, or which paints you are considering, its difficult to suggest what may work well for you. The "buffable" metallics will render a "polished," reflective look, but are also the most fragile of paints. Great care in the removal of all surface scratches & flaws is necessary to achieve a realistic metal finish, as the defects will be reflected by the paint.
Hope this hasn't scared you, but it is considered by many to be the most difficult finish to apply successfully. The best advice I could probably give is to find a paint that will give you the "look" that you want, and practice, practice, practice. (on a scrap or spare model - your newest project is not the place to experiment)
Hope this helps.