Touching up a car using spray paint?

I recently bought a white '91 Ford truck. There are quite a bit of rust spots (1-2" diameter) on the roof and the near the doors, and there's some chipped paint (3 square inch or so) near the taillights. The truck is cheap to begin with, so I don't want to spend a whole lot of money fixing this; my main concern is making sure the rust doesn't spread and having it look a little more decent would be nice as well. I can remove the rust using wet steel wool, and I was thinking I could simply cover up the grey spots using spray paint. Will this work?

I had a Dodge station wagon as a kid. I ran it through an auto car wash and discovered the previous owner "touched up" several spots on the hood with white liquid shoe polish! I always carried a jar in the glove box after that!

No steel wool, especially wet! Wet steel is what caused the rust in the first place! Use some 180 wet or dry sandpaper or a coarser grit if needed and knock off as much rust as you can. Then use a "rust stop" type primer, no need for POR stuff on this truck, just a good brand primer. Let dry, then lightly sand with about a 400 grit paper and spray some thin coats of white, lightly "feathering" the edges. When that dries you can buff and blend it somewhat, or just leave as is!

Like br549 said or even a 320 sanding block. Truck is too old to get a Dupli-Color match but you can go to Advance Auto and check out the Ford White spray. Should be real close.

Steel wool will do nothing to the rust.

At least, use an angle grinder and wheel to grind down to clean metal, treat with a rust inhibitor, then fill with bondo, sand, bondo, fair, until smooth, then primer and sanding, then finish coat.

It, s hard to stop rust once it forms! About all you can do is sand the rusty spots down to the bare metal, primer them off and use spray cans on it!