probably best bet would be sand paper.

Quickest, safest way would be to take it to a sandblaster.

look around and see if you can rent a snad blaster,, they make small ones for things like this,, it will be easier in the long run,, other wise you are in for a lot of work..
you can try a drill with a wire brush attachment,, use goggles and mask,, use those paint softeners and scrapers, again with the mask and goggles,, hey people,, that is why others charge so much to do these things,, it is hard work!! i personally use the drill and wire brush when i do this for others,,i don't like the chemicals either

There are several methods of removing paint... you can use a heat gun, with a scraping tool..or a 'paint remover', I suggest the 'citrus based'... safer to work with, or, as the others have mentioned, either sanding it off, or using a 'sand blaster'.

The sand blaster is actually the fastest method... you need some safety goggles. It blows sand particles through an air powered 'gun' to remove rust, paint, etc. It will get into hard to reach areas too. You want to do this outside, hehehe....and do not point the gun towards your home...lol.

Naval Jelly works wonders and takes off rust too. Use that as a viable option to a sandblaster which would be my choice as a professional.