-Hex Edit
-Get a completed Gamersave
-Mod Gamersave with Modio, then just beat them yourself.
I prefer using Modio, you have mods like inf. health and super jump so it's really easy to beat them all. And you can't get banned for any of the methods I mentioned above.
P.S. If you want to keep your mods for Spec Ops forever, everytime you load up MW2 go to campaign and resume and then when it comes up just click save and exit. Then go to Spec Ops, if you don't you'll end up having to mod your gamersave everytime you want to play Spec Ops with mods. Only downside though is that the only mods that ever work for me in Spec Ops is inf. health, super jump and laser beam. But it's still fun.