In addition to specific fruits like avocados and bananas, and the specific trick of using a brown bag, I would like to know if there are ways to let fruit and vegetables in general ripen faster. Are all fruits the same, or is it different for every kind of fruit/vegetable? If there is some general way or mechanism, what methods generally work to expedite fruit ripening?
A list of some climacteric and non-climacteric fruits can be found here.
It is important to note that some non-climacteric fruits (such as bell peppers or strawberries) will not respond to an ethylene treatment at all, and will not ripen further after being picked from the plant. Other fruits (such as citrus and grapes) will show ripening responses to ethylene, although they do not have an auto-catalytic production of this molecule1.
Avocados ripen in about 3 days (from rock hard) in a sack of flour vs up to a week sitting out.
Covering completely in flour has the advantage of preventing pressure bruises.
Forgetting them for a month can be icky...