This exercise is all about getting tension on the muscle at different lengths. This is why bodybuilders often talk about "training the muscle from different angles." What that really means is, you're stressing the muscle at different lengths by using exercises that have varying resistance and strength curves.
There's a couple of ways to eliminate the dead area within a range of motion of a movement. One is to add accommodating resistance like bands or chains. The other is to simply pair one exercise with another exercise, or potentially two other exercises in a giant set. The key is to make sure the resistance curve is different in movement pairings.
That's what'll happen with the bottoms-up RDL. You're going to start with dumbbells to stress the glutes from the bottom of the range of motion. There's virtually no tension or resistance in the top half of the ROM with this movement when using a barbell or dumbbells. Because of that, we're not even going to come all the way back up.
You'll descend into the bottom of the RDL and come part-way back up to make sure and work within the active range of motion.
You'll immediately switch to the low cable and do RDL's from there. You'll need to be far enough away from the machine to stress the glutes in the mid-range portion of the movement.
From there, move to a higher cable setting, which will work the top half of the range of motion, keeping a tremendous amount of tension on the glutes while they're in full hip extension.
For each movement, do 6-8 reps for 3 sets.