Slow work is very important in barrels and poles. Figure 8's and circles really help a horse. The bouncing is probably because your horse isn't pacing between poles. I never moved the poles further apart to teach my horse how to run them. I wanted him to learn on a real pattern. When I did slow work he improved 100%. He didn't blow past poles or get over excited. When you just run poles over and over again thats what the horse thinks they need to do. You have to slow down and show them its not about running and running.
When you do your figure 8's the horse will learn to change leads better and it will make it a lot smoother. Make your horse do them at a walk, trot and canter. When your horse is staying in the gait you have asked for and is turning without any bouncing or fighting the bit then your getting some where.
If you don't know how to do slow work I can tell you but I'd rather not type it if you already know how. I'll check back to see if you need anymore help from me. Good luck with what you have already learned.