Been redecorating my Bathroom

The radiator has gone a little rusty around the edges, would like to rub
down and repaint.

Question is firstly, what sort of primer?

Am gonna remove the rust spots best I can with sandpaper, then maybe put
some rust removing gel on them to get them back to bare metal. However, am
not sure of the best primer to use, bearing in mind radiators get rather
warm.

Can I get away with spraying a shot of Zinc primer onto the bare spots, or
will this crack when the central heating fires up? So should I buy myself a
small tin of Red Oxide?

Next question, top coat.

I read that dedicated radiator paint isn't all its cracked up to be, and to
stick with regular oil based paints (ive seen Satinwood recommended in
several places). So, is Satinwood the way to go?

Thanks in advance.

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Best Wishes
Simon Taylor