Easy guide to complete horde for 2 people!
Just go to day one get a handcannon each and boomshield(2 boomshields make it even easier but it's up to you.)
Go to where the torque bow and longshot respawns place a boomshield
IMPORTANT: make sure to pick up the boomshield and place it down after 15s each round or else it will disappear
And go behind the wall one of you take swap sniper for shotgun other swaps torque bow for shotgun
(you don't need shotgun, lancer is more importantly because you have a handcannon which is a mini shotgun)
And just pick em off from there and one of you keeps an eye out on the stairs and when they come the big guys will get stuck behind the boomshield (easy kills) and the little ones like drones kill em with lancer and handcannon.
(The little ones can kick down boomshields so kill em quick.)
NOTE: leave the weaker monsters till the end because when theres 1 left take the boomshields and your able to get the ammo boxes without too much hassle.

That's what me and my friend did, but we used the other side with the hammer thing. We got all the way to 50