Put some oil in your joints
Eminem is suggesting you make your flow a little smoother before coming at him.
People actually paint hash oil over rolling papers before adding weed to enhance their joints which would be a good way to reduce the pain he is going to bring to emcees who battle him.
This is also a preliminary warning to emcees to lubricate their joints and be ready to run from him considering the fact that next few bars are about rappers running away from him.
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