Charlie has a strong neck and head but I want to ride with softer hands so I don't have to tug on the reins so much to get him to turn or stop. What should I do? Is it more about using seat and legs more than your hands?
Learning to ride with your whole body will definitely improve your riding experience on any horse.
The first step in doing so is to assume a good seat. While positioning may vary depending on the activity, assuming a good classic seat is the starting point. This is much like learning notes and chords in music before trying to play a complicated composition. A few people learn to play by ear, but most learn through the traditional process.
The next step is to learn to move with your horse's movements and to keep your weight centered over your horse's center of gravity. Later, you can learn to alter your horse's center of gravity.
As your body moves with your horse's body, your horse becomes accustomed to your two bodies moving as one. Then, when you change your body movement, your horse will begin to change his to match your movement.
For example, if you are moving with your horse's body, your main cue for stopping with be to simply stop the movement of your body. While this works best when the horse is relaxed, you always want to use this cue. I don't recommend tightening your body, just stop its movement.
When using the reins in stopping, don't think of pulling on them. Think of stopping the forward movement of your hands in relation to the ground or some other stationary object. Let the horse bring your body towards your hands. In this way, the horse is putting the pressure on the reins. He has the choice whether to increase the pressure or to stop. When he does stop, release the tension as a reward, letting him know he did what you wanted.
If a horse tries to lean on the bit, I try not to get into a fight about it. I give on the reins, even to the point of letting more rein slip through my fingers. Then, as the horse lifts his head, I regather contact. I try to make him understand that I will not hold him up, and that he must support his own weight. At the same time, I am telling him that I will demand a light contact so we have a connection of communication through the reins.
When turning, I bring my outside leg back slightly and rotate my body in the direction of the turn. This is much like walking with a friend with your arm around her shoulder. You turn and she turns without thinking about it. There is no need to tug her to make her come with you. Of course, this assumes you and your partner are relaxed and enjoying traveling together. If your horse does not turn with this simple method because he is too tense, you may apply a leading rein with the inside hand. If you do so, however, you should give with the outside rein so you are not pulling on both reins and giving your horse something to lean on. Also, when your horse gives to the leading rein, relax the tension. You want to guide your horse into the turn, not pull him through it.