^^ Taking his time then Ricky.
I find the best way to tackle something like this is firstly with a small wire brush on my trusty Dremel...
Get's rid of the worst of the rust for you then with ease. Then it's just a case (as BBK stated) of going through various sand paper grades from rough (280/320) to fine (800/1000/1200) for a really smooth finish.
Then wash, prime, final coat, done.