Don’t throw your old yet trustworthy toothbrush yet! It can still be useful for other things, such as:
Remove the dirt from under your fingernails by using an old toothbrush (make sure it’s clean first, though), soap, and water.
Removing grime between tiles
Cleaning the grime out of the spaces between tiles is much easier to do with the help of an old toothbrush.
Go for DIY hair colouring with an old toothbrush for a more precise application.
Removing colour marks from walls
Use shaving cream and an old toothbrush to remove colour marks from the wall.
Cleaning the soles of shoes
Loosen up the dirt on the soles of your shoes using an old toothbrush.