You can do Bulk Hiring through any or both of the mentioned ways:
1) Place an advertisement in a leading newspaper at least 4-5 days prior to the "walk-in" interview day (include an email address in the advertisement for those unable to attend the interview to send their profiles). Set up 2 preliminary screening points/tables for shortlisting the candidates who arrive and at least 2 interview panels to conduct the technical (and HR) interviews. Additionally, you can arrange for a booth/table to handle reimbursement for all out-of-town candidates or for document collection, etc. (based on your requirements/convenience).
2) An alternative could be to provide the requirement to half a dozen consultants with a deadline by which they should send you suitable resumes. You can then review the profiles and schedule all shortlisted candidates (through the respective consultants) on a single day (or over 2 days) by allocating time slots.
3) The third option is to engage an agency/consultant who can handle this activity for your company. This would involve fully outsourcing the job. However, in such a case, it's crucial that the consultant/agency clearly understands your requirements and other details to avoid presenting irrelevant candidates during the interviews. Also, ensure your payment terms and conditions are well-defined in this scenario to prevent any confusion later on.
Hope you find these details useful. Let me know if you have any further queries.
Cheers,
A.B.