It's a matter of how thick your cavity is compared to the thickness of your layup when it's compressed to the maximum. Your layup should be less than 1,5 mm. So if you use 1,5 mm wax sheets, you should have a good flow speed. No need for a flow pattern. It will only get your part stuck to the upper mould.
As long as you are not injecting 2min resins, you should get away without pressure injection.