I believe in objective, quantifiable results. They tend to be more reliable than feelings to establish pass/fail scores.
I agree with dry firing at home, but its weakness is that you do not receive feedback. Did you hit or miss? You could also unwittingly develop bad habits and ingrain the wrong muscle memories. It has happened... The beauty of .22 lr training, when it is challenging enough (e.g. 6" plate at 150 yd), is that there is feedback with every shot and not much arguing: it either goes "ding"... or not...
I am a huge believer in .22 lr practice, and will go as far as saying that .22 lr practice is better than full power calibers practice because there is no recoil to hide the mistakes: rifle control on the sticks, trigger control, breathing control, etc. A .22 will likely show you a trigger jerk, a .300 will not...
With the R8 you are blessed with a manufacturer who understands that, and makes a .22 lr conversion for that very purpose. I bet you, they did not design it for kids...
My own practice regimen is to shoot a man-size Winchester 52 .22 lr at 150 yards at a 6" steel plate. Yep, that is quite the rainbow trajectory, but they still ring the steel when they finally get there.
The passing score is 100% hits on 5 consecutive series of 5 shots. Every miss resets the entire count. Try it, it is not as easy as it sounds...
If you can hit predictably, reliably and repeatedly (i.e. close to 100% over several months) a 6" steel plate standing off the sticks a 150 yds, there is not much Africa can throw at you that you will miss.
Because .22 lr is virtually free, I personally typically shoot 5,000 (yep, five thousand) rounds in the spring and summer before going on Safari. This is both training, and my Sunday afternoon private relaxation time in the woods (I am lucky to live in AZ where I do not need to go to a shooting range).
Once a month or so I shoot a couple rounds of whatever rifle/caliber I will take that year, just to maintain the muscle memory...
You can even do rapid fire drills at 10 yd with the .22 on the steel plate, if it is hanging from chains and can tilt when hit and direct ricochets and fragments to the ground. Quite informative too... Key operating words: go slow to be fast...