Stop Multiple Windows Service Simultaneously
The -name parameter of the Stop-Service command is an [array strings][1]. You can pass multiple services to it.

Stop-Service -name service1,service2,service3


Edit

[string[]]$services = @('service1', 'service2')
Stop-Service -Name $services -NoWait
while ((Get-Service -Name $services | Where-Object { $_.status -ne 'Stopped'}).Count -ne 0)
{
    Start-Sleep -Seconds 5
}