Hi brother, it's good to know that some wargame player do care about the first-aid during wargame time
. If you already received the first-aid training, just equip the gears you're trained to use, otherwise, it would be a good idea if you could consider to take some first-aid training course organised by St Johin, Red Cross, or AMS. Their basic first-aid skill is more than enough to handle non-fatal or minor wounding during wargame. For special police(eg SDU, VIPPU, ASDU), they are all well-trained to paramedic officer level, which mean they could even handle gun-wounding in gun-fight case, like using IV drip or IV injection for cardiac problem to stable the vital condition before the serious gun wound patient could be evacuated to hospital.