What? You can't just say that and not share the trick with the rest of us oil slicks!
Hehe. Well this is what has been working for me:
1. Drinking more water - skin more hydrated, won't over produce oil.
2. Not cleansing my face on mornings with a cleanser. It sounds semi weird but just cleansing my face with water in the morning and a good rub has been helping loads. I do my full cleansing at night.
3. Not all foundations work with mattifying primers - weird huh? I've found applying a mattifying setting powder under my liquid foundation sometimes works better!
4. My ride or dies right now are the Estee Lauder double matte and this Revlon Colorstay mineral mousse that Revlon stupidly discontinued. You can still find it on Amazon, though.
ETA: I also don't put moisturiser on in the morning if I haven't done a cleanse in the morning. It's too much for my skin a.k.a. zit city.
Hope something I've tried helps you. N.B. I live in the tropics, so this ish has definitely been working to keep my mask from sliding off lol.