I wait half an hour between doses, and I mix it with lemon or grapefruit juice, followed by nice sweet lemonade. That helps me get down all the olive oil. It's also smart to wipe out the mouth afterwards, and gargle with baking soda, so taht the lemon juice doesn't strip your teeth.
The olive oil isn't difficult to swallow at all when it's mixed thoroughly (shaker bottle) with grapefruit juice. It dissolves no problem.
Failing that, I'd trust sunflower oil more than any others.