How do you keep a pumpkin from rotting?

I'm going to be painting pumpkins for my outside display this year and wanted to know if there is anything I can do to help it from them rotting to soon. Is there anything out there that works..Thanks!

Coating the inside and outside with WD-40 or there is a new product called Pumpkin Fresh.

"People keep writing me and asking if this really works and/or if it is dangerous. The answer is yes it does really work. You spray the entire pumpkin inside and out and it will prevent rotting for a while. Keep in mind that a pumpkin will usually start to rot in about 3 days of cool (70 degree) weather and less in hot weather so don't carve those pumpkins too early.

Also, some folks seem to think that WD40 will combust violently when they put a tealight candle in the pumpkin. To them I say nope! The oil in WD40 is flamable indeed but it really will only combust when it is vaporized. Once it is on the surface of the pumpkin it won't light. Trust me, I've tried to light a pumpkin on fire in a number of ways. Just don't spray the WD40 on the pumpkin while the candle is burning."

borax or borax soap....its what the pros use to preserve natural stuff assuming you are not talking years of storage.....pumpkins are just glorified goards which are commonly sun dried. Remove as much of the meat as possible and pour in a borax soap and water solution and let them dry thourghly.....
OR
Call a hobby shop...where you can get the stuff they dry flowers