In skateboarding, when your body is really sweaty and you fall and slide while going pretty fast, thus creating a trail of sweat. You can only see this happen at a skatepark or anywhere with slick ground.
He tried to carve the coping, bailed, and his body slid into the transition thus creating a huge snail trail.
“Slug slime trail” is that of a man who “Acts as if he has a pair of vaginal lips that are dragging the ground and getting cut up so he is in pain and complaining”