How to make a job done like a fly

This cannot be done with any job you like. Whether it will be occupied by a regular or a fly-performer depends on the implementation of the job type.

The reason is that the number of performers must guarantee the maximum number of jobs to be executed in parallel on a given slave. The designer of the job type is trusted to decide whether a particular job can interfere with normal jobs or not. And if possible, he should take a regular performer. It can be customized for each job, each user may violate this warranty.

You might be able to work around the job setup issue to use a job type that you know the normal performer won't accept. Although, I haven't found anyone that would allow it to be tiring.