A true job posting "refresh" means that the posted date at the job board is updated, so the job looks like it was recently posted to Jobseekers--usually increasing the number of applicants.
A true refresh cannot be achieved by updating a job within eQuest. The refresh has to happen at the job board level, and most job boards do not support refreshes.
The common work-around is closing and reposting the job. This will result in a new "posted date", but it also results in additional transactions as it's considered a new posting by the board, and eQuest.