Hello Sangeeta,
You can do Bulk Hiring through any or both the mentioned ways:
1) Give a advertisement in a leading newspaper atleast 4-5 days prior to the "walk-in" interview day (furnish an email id in the advertisement whereby those who are not in a position to attend the interview can send their profiles). Set 2 Preliminary screening point/table for shortlisting the candidates who come in and atleast 2 interview panels who could conduct the technical (and HR) interview. Additionally, you can arrange for a booth/table to take care of reimbursement for all out-stationed candidates or for document collection, etc (depending upon your requirement/convenience).
2) An alternative could be to give the requirement to half-an-dozen consultants with a deadline by which they should send you the suitable resumes. You can then screen the profiles and call all the shortlisted candidates (through the respective consultants) on a single day (or on 2 days) by allocating time-slots.
3) Third option is to go in for an agency / consultant, who can do this activity for your company. So you would be fully outsourcing this job. However, in such a case, it's very important that the consultant/agency clearly understands your requirements and other details, so that they do not end up getting you non-relevant candidates on the interview table. Also keep your payment terms and conditions in this particular case very clear so as to avoid any kind of confusion later on.
Hope you find these details usefull. Let me know if you have any further queries.
Cheers,
A.B.