the general experience dose not have to be in ATO, does not have to be full time, dose not need Mentor to sign off, it can be accumulated if you have done 2 or more jobs, just get all your boss sign it for you for each job you did.
The requirement is on the NZICA offical website, have to be sign by an CA, and the CA have to be your boss or who knows the job you are doing, or an member of any other accounting group if the work experience is from overseas.