Hi Salmaa,
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.