It's adequate to clean egg shell to cook with it? If I want to cook natural farm eggs with its shell at low temperature (65C-150F) for 20-30mins and they have some dirt at shell is better to clean it or not?
If it's better to clean it what's the better way?
Basic food safety dictates that you always start with a clean product, no matter what you are using or how you are cooking it.  For your eggs, simply rinse with clean water, or place in a bowl of water.  A soft cloth or gentle brush could be used to remove dirt.