No problem. You can paint a car with an enamel house paint like rustoleum or tremclad. Cars used to be painted with enamel years ago and you can still in fact get enamel automotive paint if you wanted to although it's not generally used much anymore (I use single stage urethane paint wherever I can). The difference is automotive paint is catalyzed and dries harder, faster and is going to be more durable and scratch resistant. A catalyzed paint can be wet sanded not long after application if you need to fix anything. A non catalyzed paint will stay softer until you can let it bake out in the sun for a while and even then you will have to be really careful working with it in that it will never be as tough. I have used both and generally I find while a small savings in material costs can be had, it results in a huge increase in labor time to get a good result.