The fastest way to get rid of a possum is by using electronic repellents like motion-activated sprinklers. These devices startle the possums and scare them away. Another option is to use live-catch traps to capture the possum and then release it elsewhere. Securing trash cans, using chemical repellents, and installing fencing are also effective methods to deter possums. Additionally, spraying a mixture of water, dish soap, and hot sauce or crushed hot peppers around your yard can help keep possums away. It's important to remember that possums and opossums are different animals and can cause damage to plants and rummage through trash cans.