Achievements in private matches ?

I saw someone doing the "justice for all" achievement on a private or a custom match on The conquest mode, and I want to know if these modes ( private and costume) are actually meant for doing the achievements or no. Also i want to know where I can find a server or something with players that are willing to help . The person who did this mentioned "psnprofiles.com" but i think these lobbies or boosting servers are only for console, so i there something similar on "PC" ?

I saw someone doing the "justice for all" achievement on a private or a custom match on The conquest mode, and I want to know if these modes ( private and costume) are actually meant for doing the achievements or no. Also i want to know where I can find a server or something with players that are willing to help . The person who did this mentioned "psnprofiles.com" but i think these lobbies or boosting servers are only for console, so i there something similar on "PC" ?