Have rust spots on hood of my 73 Charger what can I use to repair?

I have a 73 Dodge charger that have a few rust spots on the tip of the hood,I have tried to sand and prime but the rust comes back after a few months.Do I need to have the rust cut out or am I doing it wrong?I have seen something called por 15 I believe, it's is surpose to seal the rust and not let it come back, is this something anyone else have heard of and is it any good?    

Can you post a pic. of the area.  
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It's hard to tell the extent of the pitting without photos.  If you could post some I think I could help you out.  You never actually get rid of rust on a panel without replacing it.  You just cover it up and try to keep oxygen and moisture from coming back into content with the metal.  When you patch you are create a new spot for moisture and oxygen to get in and start corrosion all over again.  If done correctly it shouldn't matter otherwise you'll be in the same boat in a couple years.  It sounds like you don't want to replace the hood yet so your best bet would be to try wire wheeling the rusted area.  Try to use as fine of a wheel as possible.  Take out as much of the color as possible (all of it would be best) because this is where oxydization is taking place.  Once you have everything taken out and it's all clean spread a real thin layer of duraglass or another brand of filler with ground up fiberglass in it over the rust area.  This will keep most of the moisture out of the area.  Sand it flat with 240 grit sand paper and make sure to feather the edges out.  When you're done with that spread another thin layer over it but this time with glazing puddy.  It's like bondo but creamier and a lot smoother to spread.  It's not used to fill dents but to eliminate major sand scratches and flaws.  When dry sand flat and smooth with 320 grit paper.  Again make sure to feather out the edges.  Now you're ready for primer.  Make sure you get primer on right away so the metal doesn't start oxidizing again.  With the hot humid weather coming up it won't take long.  I had a 71 Mustang sit in the shop over a weekend with some bare metal showing.  It was last summer and when I came back on Monday the metal already had a good amount of surface rust.  If you need any more questions asked just let me know.  

If you need help posting a picture send me a PM and I will guide you though the process.