CLR works well for superficial surface rust. As a base clean-up it can be a good start. Applying a clear coat over the surface rust that's left after cleaning can "lock" it in and protect the sheet metal from rotting further. A lot of people use a linseed or teak oil to "rub" in for a semi-gloss shine.
Be careful with the term, "patina". I'm not trying to be a douche here... but the original idea of patina came from the natural wear and overall affect of time taking it's toll on factory paint. In all reality, it's an earned process. When manufactured to look like it has natural patina, it loses it's definition and uniqueness.
You have to be lucky enough to find patina. If you force it, you've lost the concept all together. Layering paint and then sanding it off can look great. It's a way of painting a car to make it look old and used. But if it's not natural, it's not technically patina.