I do something roughly similar before a trip that might require unsupported or semi-supported field shooting (Africa, etc.). When I book such a hunt I usually take a light and a heavy rifle that are shot both offhand and from sticks. I shoot ten rounds at each of the four targets at 100 yards and five rounds at each of the other four targets at 200 yards and use each target again for five weekly range sessions. What I end up with is two 100 yard off hand targets and two 100 yards from the sticks, each with fifty rounds fired, and the same with the 200 yard targets with 25 rounds each. The targets are taped on my wall for inspiration and analysis. This is done for about three months and hopefully the groups shrink to an acceptable level. Of course the targets shot with the lighter rifle look a little bit better than the ones with the heavier rifle. Unsupported shooting can be very humbling but with proper practice it can be improved.
For North American hunts I can always find or improvise some sort of rest or solid sitting position so I do not use much range time shooting unsupported.