1. Put unit in the editor and name it "guy" for example.
2. Then try using one of these:
http://community.bistudio.com/wiki/forceWeaponFire
http://community.bistudio.com/wiki/fire
http://community.bistudio.com/wiki/ArmA:_Actions#USEWEAPON
They should work.
3. Play some animation by switchMove command, for example: guy SwitchMove "acts_CrouchingFiringLeftRifle01"
4. Try those three commands again.