As people have said before, fireworks will work and also sea salt in a spray bottle filled with water. Experiment with the level of salt vs water, but for that look, I'll say salt: 80% water 20%. Amonia and salt work wonder also.
Is it a rare item? If it isn't, then I would experiment with different solvents and a heat gun to fade the paint on the outside. If it is rare, and therefore you're only going to get one shot at it, I have nothing to recommend for fading the paint as it's not something I've done before.
Do some white paint washes and then adjust the washes as needed. Then start using some weathering powders or oils paints for the rust and finish off with some airbrush effects.
I agree with Mr. Bolo, but would add that I would begin with a light sanding of the entire surface. A Harbor Freight sandblasting airbrush makes short work of this kind of job. Go slowly, either way!
This can isn't white washed, it's sun faded. You can tell by looking at the areas that are white.
I apologize if this comes across as pompous, but rusting a can is fairly straight forward. I'm more specifically looking for a way to make a painted steel can look sun-faded.
I would take 400 grit sand paper or higher and gentle sand down the color. Then use steel wool to buff it to eliminate any sand paper marks. That should lighten it up and maybe show a little steel in places. That could benefit you when you rust it. I have even had great results just by buffing the paint with steel wool and no sand paper. It really knocked back the color of the paint well.
There are many formulas online to achieve the rusting.
I have soaked the metal and left out in the humidity overnight to start the process.
I have then soaked items in amonia, salt, lemon juice and vinegar and left it outside for a couple days and it rusted anywhere that the exposed metal was touched by the mixture.