I pull the shock shaft all the way down then fill with oil. I then push the shock shaft up about half way, then I put it into my Ride RJ600 air bubble remover and pump those air bubbles out in two seconds.

If you don't have an air bubble remover then I would pull the shock shaft all the way down, fill with oil then push the shock shaft almost all the way up then pull back down and wait until all the air bubbles rise to the top by themselves.

Take Care,
Cheers, Patrick