mate since you have paid for the job NOT DONE, ask him to reopen, clean the clipper wash the piston with acetone or petrol to clean clipper shims further & ONLY use BRAKE CLIPPER GREASE [ Permatex is brand name] you can buy other brand from plaza autoparts market,. That grease tube / tin will remain your property after the job is done for FREE.
locate a new mechanic who knows how to perform a quality job with right specs & tools.