Painting Metal Trailers

I have 25 older metal units in my park which could benefit from new paint. Some have spray painted address numbers, one has grafitti and the others are either faded or multicolored. They remind me of the 1970 plymouth duster i drove in high school. They are however all full and fairly solid. They are all tenant owned except for 2. I have started to bring in newer 1999 and 2000 models which make the older ones look even worse.

What type of paint is best for metal? enamel, latex, etc.

What kind of prep work is needed? wash with bleach?

How much paint would a 12x60 need if sprayed?

I plan on paying for this myself to beautify the park to attract new tenants.

Thanks to anyone who can take a stab at this