Turn on hood fan
Spray the oven with Easy Off,
Close the oven door right away and let it sit for a few minutes
Wipe off the grease with a scrubbing ball and paper towel
You can use a mask to protect yourself, I usually just hold my breadth.
If it's very very greasy, use the self-clean cycle built in your oven (most ovens do have self-clean capacity). It basically burns all grease to dust, takes about 3 hours.