Find two empty terrain grids, and move between the two. Bandits and creatures spawn when you enter an empty grid that has no bandits or creatures already on it (and they disappear when the last PC leaves the grid.)
A sprint is nice and fast at moving between grids. You can also put a bacta tank in one, in case you get dangerously wounded and need healing (but levelling up also restores HP). And the sprint holds a decent number of NPCs. You may need to swap NPCs if they take damage, and let them recover. I sometimes put my damaged NPCs into a squad and make them patrol, and as they level up their HP is restored.
I also place 'spotter' NPCs on the two terrain grids, with sensor packs, and carry one myself. This way I have full sensor coverage of the grid and can immediately see if there are any bandits or creatures there.
Even if your NPCs have no weapons in range, its useful to have them in your party, as they may take some hits and this helps spread the incoming damage.
I usually use a single shot sniper rifle (A-280 or X-45) while staying out of range of bandit or creature weapons (great for XP), or a full party all using Bowcasters when its safer and I need to get in closer for a quick kill. I sometimes equip a party a with A-295s for a slightly longer reach.
Any weapon on an NPC that dies is lost. So be careful about giving them your best weapons.
I've also recently been using Criminal NPCs, so I don't feel so guilty when they die in combat.
There is no god but Ara... All will walk his path...
The Faithful of Ara
<--- (Warning: music link)