I used to be pretty oily and found that stopping the oil is far easier if you strip your skincare routine back and try to treat the problem.
Using an oil off cleanser or a foaming cleanser can really help to get rid of excess grease, I put the cleanser on my skin, let it sink in and then wash it off.
Apply moisturiser as you need and you will see that you have a lot less oil to contend with. If you still need powder it will be less than you originally needed.
I'd recommend Rimmel's Stay Matte range of powder, they were the first powders I used and they are my HG, plus they last ages!