There is no seal, this is why they tend to use oil, all you need to do is to fill the oil inlet hole with oil and let is dissapear a few times, this will take 20 mins max, spin the turbo by hand when doing it as it will help draw in the oil.
The pressure inside a turbo tends to stop so much oil being used, if he's used thin oil it most likely appears worse than it is.
Just let it idle for a few mins when started just to ensure a nice supply of oil.
tabetha