Turn the shirt inside out
Brush off any dry residue with a soft cloth or clean toothbrush
Mix equal parts white vinegar and water
Dampen a clean cloth with the solution
Gently blot the stain
Let it sit for 10 to 15 minutes
Rinse the area with cold water
Rub a small amount of liquid detergent into the stain
Wash the shirt in cold water
Use a detergent safe for dark colors
Air dry the shirt
Check the stain before using a dryer
Repeat if needed
For stubborn stains, make a paste of baking soda and water
Apply the paste to the stain
Let it sit for 10 minutes
Rinse and wash again
Avoid bleach
Avoid hot water
Avoid drying until the stain is gone