The secret to better engagement and activity is really not to do anything with your seat that can block or slow down the hind leg movement. “Take the foot off the brake, before you step on the gas” is something I used to tell students who took longe lessons on our horses in the US and weren’t able to keep the horses in the trot. Most of them would immediately kick the horse to keep him going, although they themselves were the reason why the horse fell back into the walk. The less you interfere with the horse’s back movement, the less you need to drive.