what I did, and found it really simple, is I used a wire wheel as mentioned above, hooked it up to my angle grinder. (I first tried with sand paper but took me forever and a day to get a tiny piece done!)
mine was pretty badly rusted everywhere...
For the smaller, hard to reach places, I used a Dremel hand tool with a wire wheel tip on.
After that, I took a steel brush with Liquer thinners and finished it off. That helped to eat the last of the rust off.
Then I re-sprayed it with heat resistant spray, and voìlà! looks good as new!