i wouldn't hold your horse back, it'll just get more wound up.
Try exercises. it's actually really good fun and help make a hack into a 'schooling' hack. - progressively getting harder, here are some ideas.
riding along in a line, start your horse where it is comfortable. you could do rear file trot to the front, your last horse trots passed the others, giving a reasonable space so no one gets kicked and takes up lead, everyone takes turns at being at the front and at the back for a short period of time, not too stressful, when you are experts you can do it in canter etc.
or you could do lead file turn and walk to the back, again, everyone takes a turn.
you could halt in a group and get each horse to trot away a short disance and and walk back, when you are happy with the control you could canter away and trot back, when you have enough control try a steady canter back, you could canter away on one lead, canter back on the other, canter away pop a jump and walk back, use your imagination.
you could walk or trot along as a ride, lead horse halts or walks, the rest pass and horse joins on at the rear.
these are great exersizes for teaching riders to control their horses independantly and brill for teaching horses to go anywhere in a ride, they are only asked to do things for a short period of time and it gives them something else to think about rather than just fixating on the tail in front. we used to use these all the time in the riding school where i worked and this resulted in my horse whom I often used as a lead horse, being a total angel, out on hacks now, he'll go at the front, the back, in the middle, and if our buddies take off, he doesn't go till i tell him he can.