In Canada we have a choice of Rust-oleum or Tremclad (owned by Rust-oleum) products. If there is a difference I couldn't tell you. But I can say that Tremclad makes a 'rust' paint for use on aluminum. There was no mention of a primer requirement; however, I did clean the pipes thoroughly.
Rather than remove the intake pipes (on a 928), I simply took the head off of a small foam brush, soaked it, squeezed the excess out and rubbed the paint onto the spider.
Here's how the first coat turned out:
