There are many reasons for your skin to have open wounds such as trauma, diabetes (always below the ankles),vein diseases and pressure (bedsores).  With so many reasons (and many more not mentioned), it makes sense that just applying a simple dressing to the wound would make it heal.  If your Aunt Tillie used a family made cream to treat her insect bites, it is unlikely that this will work on a more complicated diabetic wound.  Some simple recommendations are to always make sure that there is a definite diagnosis for the wound.  Bedsores and vein ulcers (between the ankles and the knees usually on the inside of the leg) are from very different causes and so the treatment must be different.  One rule of thumb is to make sure that the dressing helps and not hurts the healing.  And so, if you would not put a specific dressing or ointment in your eye, then do NOT put it into the sore.  Also, "Letting the air get to it", is a bad idea as this makes sores dry and dry is not something beneficial.  Remember, we put people in the hospital when they get dry (Dehydration) so why would anyone think this was a good idea.  Keep the wound moist and the surrounding skin dry is the modern adage.  Modern wound dressings should be changed every other to every third day depending on how much drainage and how "dirty" the are gets through normal activity.  This will actually decrease the risk of infection as it allows the wound to establish its own environment and grow new healthy tissue undisturbed.
Any wound or injury  below the hips thta is not healing normally should be evaluated by a health care provider getting an arterial assessment.  If it does not have blood supply, it won't heal.  Most wound dressings will have excellent healing potential beyond their date of expiration.  The FDA mandates a date to assure safety but a sealed dressing kept in a safe place will still work for some time. And so, when buying or looking at a wound dressing, ointment or bandage, make sure it won't hurt the wound, can stay on 2 or 3 days and is appropriate for the type of wound you have.  When in doubt, ask a real wound care specialist.