I have several small rust spots that are mostly on surface - not deep holes.  A body shop has quoted me $200 to buff and repaint them.  I don't want to dump a bunch of $ into it if I can do it myself. 

I have no experience with touch-up painting, but willing to do it myself if there's a way.  It doesn't have to be perfect -- a fairly old car.  I already have paint from another touch-up done 2 years ago.  Another post mentioned to start with a 'rust converter'.  Not sure what the steps are in this.  Please respond if you can help me out.   

See https://www.paintscratch.com/neworder/store/item/mar/Rust-Away/ and this will tell you about the rust converter. Sounds like you will need primer, paint and clearcoat also.

here is the product I have used in the past with very good results

http://www.stoprust.net/por-15_faq.htm