Practicing with your dog is great. Whether it be the entire routine or just certain parts over and over, it all helps. But to keep the dog's health and safety in mind, you truly should limit how much you work your dog in any one session or day.
But then there's the practice sessions you should be doing, just by yourself, where you can spend quality time working on your various releases and distance throwing for toss & fetch. I have made the habit of practicing my throws and releases during my lunch breaks at work. One tends to spend a lot of time working your throws and you don't really want to torment your dog or even throw to your dog for too long a period of time. So solo practice is your best bet.
Since Toss & Fetch is still a critical part of this 'Open' division, you need to give it some thought and practice.
First, find yourself some field cones or something to mark a field with... it doesn't matter what. Heck, even extra discs will work.
For practicing purposes, I'd mark out a field somewhere. If you don't have a tape-measure, that's fine. If you can figure out how many feet-per-step your pace is, you can pace out a T&F field, length-wise. I'm six feet tall, so taking solid steps, every two steps will cover about five feet, and you can pace out a field. It does not have to be perfectly accurate because it's not technically the distance we're working on, but your aiming processes as you specifically work on aiming for a specific distance or point on the ground.
The first trick is to work on a relaxed grip and release.
When lining up, for right handers, turn so you are facing 90 degrees off to the left of the field direction, with your throwing shoulder 'pointing' down the field towards your target to work your tosses. Of course, left handed players, it's opposite. Pointing your shoulder towards your target zones helps you rotate through your release, which is the preferable method of delivery.
Set your target, whether it be a spot on the ground, a lounge chair or what have you, out there.
The premise behind getting your body into the shot is to save your arm and preserve your shot. If you're shooting all arm, you are using too much arm muscle. If you're using all muscle, that can unintentionally force you to muscle your grip. Gripping too tight can hinder your release timing, sending your shot in directions you're not emotionally prepared to have it go.
We've all done it.
If you have to shoot for shorter ranged targets until it works or feels better, so be it. Heck, there are days I go out, and work on 10 to 15-foot target ranges to keep my aiming aparatus (the brain) tuned into the basics. You know the saying, practice makes perfect. And Bruce Lee used to push getting excellent at the basics as your foundation.
But all in all, your initial minimum goal is that 30-60 foot, one-point range. And to not use all-arm to throw a disc.
The One-Point Zone Practice
For the one-point practice shot, you want to aim for the center of that zone, or 45 feet away. I don't want you practicing for exactly thirty feet because if you get in the habit of landing it at 30 feet, the dog may grab at the disc at the 25-foot point, or the zero-point zone. Doh!
So start executing your shot for that 45-foot range. When executing your shot, work on reaching out towards your target with your follow through. Reach out to the direction of your target and once released, letting your arm do it's own follow-through.
You'll see a lot of people, when they chuck the shot far, end up with their chest facing the target. But before that, they had rotated through their release to get there. But regardless of the shot, try not to be only or ALL ARM. You will be more consistent with a loose, comfortable delivery.
I've watched people stand perfectly rigid and use only their arm to throw a shot. If it works for you, great, but to use more of your body to help impart speed and distance makes the entire process easier.
The rotation of the hips, the arm pulling through, swinging, reaching for your target, letting the disc spin off your fingers during the release are all components that add up to speed and/or distance.
I will wag my discerning finger at you with a disapproving look if I see all arm shots later!
When practicing, you can make T&F practice a truly effective practice.
You can do that in the following fashion: Once you've thrown however many discs at your T&F target at whatever distance you are working on, go collect your discs at that distance, then practice one type of FS throw back toward your starting point.
Now remember, FS throws don't really need to be more than 30 feet, so if you just practiced a 60-foot T&F, then that can add up to two rounds of FS practice tosses! And if you are at least 60 feet away, you can practice your dominant hand for the first 30 feet, then if you want, your non-dominant hand for the second 30 feet.
I personally work a single kind of FS toss back to the starting point, no matter what the distance. So if I just practiced my 90-foot throws, I have two or three rounds of FS shots to work on getting back to the starting point. And it's good exercise with all that bending over to pick up discs. (I throw at least 10 discs at a time.)