plasticote will normally tell you on the side of the can whether or not you need lacquer, even if you don't though it shouldn't hurt, as its going to get bashed about. also it will tell you what colour primer to use to get the best out of the colour pigment.
biggest thing to remember to use especially if your going onto metal first is a light dusting of etch primer (zinc primer) first. it'll bite to the metal more so it won't flake, then normal high build primer, flat it down with wet and dry, (no need for a base coat) then your flat coat, lacquer probably optional!