The list mentioned by you like ads,reference,campus and sourcing through portals are the only ones for recruiting.
May be you can try issuing flyers a similar one to advertisement.
And quick hiring depends on your type of profiles required,consultant or your recruitment team (strength) support,project type etc. If you compromise on specs like experience,exposure,type of industry etc may be you can get quickly.
Even a single recruitment, if specs are clear and skilled personnel are required takes more than the offered/standard time in recruitment,then massive hiring can be a big ask always.
4th April 2018 From India, Hyderabad
4th April 2018 From Pakistan, Lahore
Even if it is a project of engineering, some kind of experienced personnel are required during installations,start up etc, Campus recruitment is for freshers and the need for them to be trained to meet your requirements is on you (Management) again.
Massive hiring can be done through it, but have to check stability factor also.
5th April 2018 From India, Hyderabad