gistfile1.txt

 $filter = "2k12R2\\amd64"
 $drive = ((Get-WMIObject Win32_Volume | ? { $_.Label -like "virtio*" }).Name)
 $drivers = (Get-ChildItem $drive -Filter *.inf -Recurse | % { $_.FullName } | Select-String $filter )
 $drivers | %{pnputil -d $_ }

gistfile2.txt

$winre = (Get-ChildItem C:\Recovery -Filter winre.wim -Recurse -Force).FullName
cp $winre C:\winre.wim
md C:\winre
Dism /mount-Wim /Wimfile:C:\winre.wim /index:1 /mountdir:C:\winre

$filter = "2k12R2\\amd64"
$drive = ((Get-WMIObject Win32_Volume | ? { $_.Label -like "virtio*" }).Name)
$drivers = (Get-ChildItem $drive -Filter *.inf -Recurse | % { $_.FullName } | Select-String $filter )
$drivers | %{Dism /Image:C:\winre /Add-Driver /Driver:$_ /forceunsigned}

Dism /unmount-Wim /mountdir:C:\winre /commit
mv -force C:\winre.wim $winre
Attrib $winre
Dism /unmount-Wim /mountdir:C:\windows /discard
rmdir C:\winre