At Westside we routinely work the lockout of the pull. A rarely performed variation is the isometric portion of the lift, which we do in the ATP to directly target the hips and glutes.
Load 80% straight weight of 1RM Sumo/Conventional Deadlift, with additional band tension based on level of intensity desired on the carriage. In your Sumo or Conventional stance hold the glutes tight for max time until the glutes release.
Check this beast out...