Easy to boost with one or more friends.
Just create a private match in King of The Hill and invite your friends in it. After that just take turns and win 10 match in a row.
2 things to specify.
Creating a room is not the same thing as to create a player match. A room is for chatting and challenging anyone in it.
Someone who disconnect give you a win but it DOESN'T count toward the 10. If you got kick out of the room because of this you will have to pick up from where you where and not from 0 thankfully.
As a side not, since you are in this mode boosting might as well give the winner a note of 10 to work toward the 2 other achievment that ask for a certain player rating.