I dont believe him with that LvLing "haxx".

I play RETAIL CoDMW2 on PC via Steam, the only things Ihve found usefull for not destroying the fun is EAM (easy account manager) and PSE (player stats editor).
EAM is used to export and import the stats from and into the game.
PSE is used to edit your experience, kills, deaths, headshots, weapon ranks, unlock titles and emblems and set the prestige and some other stuff.

That is the only "fun" way ihve found to maybe skip a level or two.
There is no fun in skipping 710 levels (70 is max but to prestige you need to completely level 70 to 70 with 99.99%)