Note that this recommendation is for total weekly volume, which means it would need to be divided up based on how many times you’re training each muscle group per week. So, for example, someone training everything twice per week would do 30-70 reps for each bigger muscle group in each of those workouts, and 15-35 reps for each smaller muscle group in each of those workouts.
Why less volume for the smaller muscle groups, you ask? Partially because they are smaller, but mostly because they get a ton of indirect volume while training the bigger muscle groups (e.g. your biceps get hit pretty hard while training back, triceps get hit pretty hard while training chest and shoulders, shoulders get hit pretty hard while training chest, etc.).
Any exercise that works and/or stretches the buttocks is suitable, for example lunges, hip thrusts, climbing stairs, fencing, bicycling, rowing, squats, arabesque, aerobics, and various specific exercises for the bottom. Weight training exercises which are known to significantly strengthen the gluteal muscles include the squat, deadlift, leg press, any other movements involving external hip rotation and hip extension.