Painting balcony railing advice

[jadee]

Hi everyone, 
My condo's balcony has a metal railing, it's painted white but has some rust. In some places the paint has chipped off. I'm just looking for some basic advice. I live near a Home Pro so if anyone can suggest products there, that would be helpful. 
1) do I just use sandpaper to sand off the rust or do I need to strip the paint? If sandpaper, what grade of grit is best?
2) I've been to Home Pro and noticed spray paint cans of 'Rust-olene'  that claim to be a 2-in-1 primer and paint - could I use that to repaint? If not, what type of paint do I need? If anyone knows the brand name/type that would be helpful as I'll know what to look for. 
 

[Langsuan Man]

You must be in Pattaya since the Home Pro on Klang at Big C Extra is the only Home Pro that I have found that sells Rust Oleum

 

If you just want to do a "spot" job then the Rust Oleum 2 in 1 aerosol would be acceptable,  just get "flat" white variety and a fine grade of (metal) sand paper would be OK.  My only concern doing a spot job is whether or not the Rust Oleum white will match your current paint 

 

I recently re painted a large patio railing so I used an orbital sander to get rid of the loose paint / visible rust and then used Rust Oleum "Rusty Metal" Primer followed by Rust Oleum Flat Black, expensive using Rust Oleum but at least I won't be doing it again for at least 5 years