2 answers to your question regarding home made oil. Its possible to buy and amazing oil expeller from www.piteba.com it is designed fro pressing ol from seeds, such as sunflower seeds, and has a fairly high yield. It is designed for 3rd world micro business, so people can make and sell oil and oil seed cake for feeding livestock from their own grain. It will make great oil from sunflowers (the black seeded ones).
The other answer is for the olive oil.. Lay your fresh olives on a tray in the sun for 10 days to dry, turn them twice a day.
Use a cider press to press the oil out.
Line the cage of the press with a nylon mesh bag. Fill to within 3 cm of the top. place a bucket under the spout. Ratchet down the press. bright green oil will start flowing out. Keep the pressure on until there is no more oil coming out or you hear the pits start to crack... they make it taste bitter, so stop then. Let the oil settle. Any water present will be at the bottom. The drying process you started with should have eliminated most of the water though. You can use your oil immediately.