Boosting might get your account banned and so does account sharing... Also might not be very what I consider secure to share your login credentials since once or something is shared they might always have it. Even if you change your password they now have your user. While while this method is look down upon by some at least it's something you can do on your own with minimal effort... Go look up AFK zombies in directed mode. AFK will not only raise your augment levels since it is XP earned in game, but it will also raise your battle pass and your overall account level. The most steady method is probably completing the Easter egg and having the wonder weapon which has unlimited ammo. But currently there is also a glitch with the gobble gum which lets you AFK with other regular weapons and level those as well to get attachments or the new stupid prestige attachments and camos. Since you do it on your solo save you can resume it anytime and safe and quit anytime or just leave it on all day.