I deadlift the same style and lockout is quite a bear at times. Big benefits being decreased distance and speed off the floor. Granted I never really peak a lift doing strongman, you do have 24 days to work with. Some things that help me are mid shin rack pulls with lots of band tension (cutting back on them now). I started out with abou 200lbs of band tension but now use 315lbs of tension. This hits the glutes and upperback is a lift specific way. You may do heavy rows and shrugs to hit the upperback but they aren't hitting that area the way they are stressed with the rounded back pulling stlye. As for getting the hips through at the top (notice how the legs lock and then the glutes lock) some things that have been helping me with that is wide sumo stifflegged deadlifts and wide stance box squats (both heavy and speed with bands). Also helps having some yelling cues to you like HIPS!. Internally yelling that if you catch yourself sometimes helps me correct mid lift.
"Strongman is stupid."
- Mike Jenkins