Sal Suds has been the best “more natural” solution I’ve used to remove grease stains, and the process of using Sal Suds to remove grease stains on my shirts and shorts couldn’t be any easier.
Rub a small amount of Sal Suds on a fresh grease stain, using a towel or your hand to thoroughly rub the grease area with the soap. It's important that the soap saturates and completely covers the grease stain.
Let the Sal Suds rest for at least 30 minutes-12 hours (I usually let the soap sit on the grease stain for the full 12 hours, which causes the soap to fully dry.), then wash the garment in hot water in the washing machine with laundry soap.
Before drying your garment, check the grease stain to make sure it’s completely gone. If not, apply the Sal Suds again and allow for more resting time. Repeat the washing cycle again until the grease stain is completely gone. The key to fighting a grease stain is to never dry a garment in the dryer until the grease stain has been removed. Drying a garment sets the grease stain, which is trickier to fully remove. That said, I've successfully removed grease stains using Sal Suds and a 12 hour rest time even after drying a garment.