A man recently died while attempting to assassinate Donald Trump, so there is no better time than now for a quick refresher on how to sustain the ghost of a dead person whether they are related to you or not.
As a reminder, you can use coffee, water, or various types of prepared food to sustain the ghosts of the dead. Even candy or other snacks are good as long as they are offered in the form that they are ready to be consumed in. This means no raw meat or unpopped popcorn. Liquor can be good but is mostly used for those who dealt with alcoholism in their life, and might cause the ghosts to become drunk and less competent when interacting with the land of the living.
You should be protected when doing this in case the ghost decides to turn on you, but this is unlikely if you are providing them with sustenance to interact with the world. Imposter spirits are a risk but unlikely if you know exactly who you are giving an offering to.