To flush blob cache on SharePoint servers you should execute a PowerShell script on each front end server. Blob cache is set on each front-end server in a farm, that is why you have to do this way.

Of course, you can use 'Invoke-Command' to execute script on other servers. The script to flush blob cache is here:

$webApp = Get-SPWebApplication "<WebApplicationURL>"
[Microsoft.SharePoint.Publishing.PublishingCache]::FlushBlobCache($webApp)
Write-Host "Flushed the BLOB cache for:" $webApp