1)have a full squad of 8 soldiers
2)have grenades/grenade launcher
3)most wilderness maps have rocks that provide cover and/or long range sniping positions
4)clean up anything close enough with GL bursts, MG full auto, Bolter bursts, grenades
5)clean up anything unarmored at long range with laser weapons
6)at this point the aliens should be few enough that you can use medkits to heal damage done, find those few bits of cover, and shower them with laser fire until they close enough to kill with something more deadly.