Drying chiles is a well known method (at least in Mexico), of preserving chiles, and it is a method that is probably unacceptable anywhere else..
There are two important steps when dealing with the preparation of the fleshy chiles like anchos. mulatos, and pasillas for thick moles, they should not be soaked for long periods of time, or their flavor will be left in the soaking water.
Second, Never attempt to skin the chiles once they have been soaked, the skin provides flavor, color and texture (acting as a thickener agent)
CHOOSING AND STORING
What I recommend when it comes to choosing and storing dried chiles is that you should always buy chiles that are loose, so you can see what you are getting. A dried chile should be dry but flexible at the same time, if the chile is too dry it will be hard and crumbly and this translates to more time soaking in water and only after that you will be able to remove the seeds and veins. If you try to clean them before soaking they will crumble in your hands.
Avoid chiles with transparent patches of skin; a fruit fly has been at work and eaten the flesh from the skin. It has probably also laid eggs inside and in time, with the right conditions, little grubs will hatch out.
Your dry chiles can last for years when stored properly. I recommend storing them in a cool, dry place, your fridge or freezer are great options as well.This will prevent insects from getting at them, but no matter where you store them always open one up and see if it has any traces of mildew. if this is the case throw it out or better yet, burn it in the oven, then dispose of it.
Chile de arbol
Many people may think that the chile de arbol comes from a tree as its name implies but from a tall plant. It ripens from a gree to a bright red and retains its color qhen dried. It is a long, smoth-skinned, thin chile with an average length of 8 centimeters (3 inches) and it is very hot.
This chile is mostly used for table sauces in some occasions it will be blended with other more fleshy chiles for meat stews. It is available here in Toronto in Kensington market.
Never, ever clean the veins and seeds of this chile, it is supposed to be hot, you can either (tatemar) toast the chiles on a hot comal or cast iron skillet, turning them constantly until it is lightly browned and crisp or heat a little bit of oil, add the chiles and fry until lightly browned and crisp. Do not soak. Place it in the jar of a blender or follow the recipe instructions.