Well, it's really up to you. In the field German armor was painted with whatever paint they had and camo with whatever paint and brushes or airguns they had available. So either or will do. If you want more of a "Tiger" look then use a regular paint brush or very very fine line using an airbrush. It all depends on what you like. I have seen both ways done in a very very successful way. You might wish to check out some sites like...
http://ww2modelmaker.com/default.htm
... I'm pretty sure you can find examples of both methods here used on models.
-Greg