Hi,

The first option does not give you any guarantees.

The 3rd option is quite hard to execute and does not have any additional pros if the person who makes a referral is based locally (usually he has to select several offices you are applying to anyway).

Definitely, the 2nd option is the best one:

1. The consultant makes you a reference in the system and uploads your resume. Usually, he has to indicate why he thinks you are a good candidate
2. You skip some steps in the recruiting process (CV screening at McK, Test at Bain)
3. The consultant gets a referral bonus ($) if you get a job offer

The conversion to reference will be higher among consultant / manager level people who are still interested in the referral bonus. The basic idea is to ask these people for a mock interview.

Good luck!