If you absolutely have to do this, get a compressed air blower nozzle thingy. Have a pan handy, you might want to get some help, it will come flying out. Oh yea, wear some safety glasses, since you are going to make a hell of a mess.
that would be the fun way
the other way is to take a lube pump and stick the feed end in the plug hole and hope you can get it to draw some up, im not sure this will work all that well though, but a lube pump is like three dollars and they come in real handy for refilling. I use the bigger type that goes on a gallon jug, i rinse out a old antifreeze jug real good. then i pour the three quarts or whatever into there and use the pump with a rubber hose hooked to it.