Since no one came up with any other strategy than the one I employed to get it, here is what I did.
My strategy is to first start a game with:
- Victory Point Limit: 99999 (or higher, if possible)
- Fully stocked
- Party Wagon
- Llama Pile
- No Quarter
- Activate the mod: Achievement_Farming (by Mikey Psycho)
The mod will create a really large map and increases the number of scientists in each mission.
I then play one mission, quit & save and then activate another mod:
- 1_zombie_per_wave_v2 (by rancorblood)
and continue the game with it, which makes the missions really easy and all 1 and 2 missions can be finished with a gold medal in only a few seconds. You need to bring along:
With that, you should be able to complete 90% of the missions in under 20 seconds receiving a gold medal.
But the whole XP counting, points counting, flashy animations, etc. is annoying. Most of them can be shortened by pressing left or right mouse button or ESC.
I'm estimating 1 minute per gold medal right now, I played the game a total of 25 hours.