the first glitch is pretty easy to do and the second one isn't even worth trying. if 2 zombies come at you in the second glitch you usually fall down the slide. in the first glitch, once you get in it, make sure you dont stand or crouch. just stay prone and slowly turn around when you land on the slide.

also when you do the first slide glitch, the zombies dont pile up, the just dont go for you. also it is extreamly easy to fall out of. if you move around to much or sometimes even shoot too much you'll just fall right out. but its good if you want to go like get a sandwich in the middle of a round