Overly roomy size 12 shoes don't have to be discarded or donated. Take advice from some shoe experts to shrink them. You won't get from a size 12 to a size 6, but if you want to shrink the shoes one or two sizes, these methods should work. Use leather shoes only; shoes of other materials may be damaged.
Soak the shoes in water. Shake out any excess liquid.
Put the wet shoes in the clothes dryer on a drying rack. Set the dryer to high. If you don't have a drying rack, set your oven to low heat. Place the shoes on the middle oven rack.
Leave the shoes in the heat until they are dry. Check the dryer or oven often so as not to scorch the shoes.
Remove the shoes from the dryer or oven.
Treat them with a conditioning oil.
Try the shoes on to see if they now fit.
Soak them again if they still don't fit. Repeat Step 1 through Step 6.