Glutes - practice
The point of the glutes drill is to make it autonomous - it should work in your sleep.
Position on the bike depends on the amount of resistance on the pedals. If the pedals can support your body weight, get your body weight on the pedals. If the pedals can’t support your body weight you’re going to need to sit up a bit. Cadence should be determined by physics. If you replaced your body with a sack of potatoes, the cadence shouldn’t change. Learn how to just get your full body weight on the pedals, fall into the pedals.
People sometimes move side to side. This is something learned from walking because your hips rotate when you walk. On the bike you have a triangle made up by your feet and your center of gravity. Your center of gravity should never get outside of your feet. While there is some side to side, it’s pretty minimal. Those pedals are directly under you.