You can get the "Helping Hand" achievement pretty quickly and easily if you set up a local multiplayer match against 15 bots with the maximum time (I think it's 30mins) and maximum kill limit. Make it a Dogfight, not team dogfight, as you go against all 15 bots and any damage they cause between themselves can go towards your assists. I managed to get this achievement in bout an hour or so.
Also works for "Sky King", winning 25 multiplayer matches, "Flawless", although I'd set the kill limit to 25, "Weaponeer", and "Classic".
: Stuffed shirt usually very empty person
ROCK IS BETTER!
Retail Complete: 27
Arcade Complete: 21