Mask clearing was my hardest skill, OK well that and perfect buoyancy in 10ft of water. A few tips for you that helped me that weren't so clear from some instructors:
1) Low volume mask, why make it harder than it needs to be?
2) Press on the top of the mask only, being careful not to lift the bottom
3) A steady, smooth nose blow is much more effective than a fast blast such as one would use to clear a snorkel.
4) Look up, as in at the sky. I see those who advise not to do so but it works great for me.
5) Don't be in a hurry, take your time. If it takes multiple attempts, so what?! If water gets in your eyes when you open and have discovered you weren't successful, so what? If it takes a couple of minutes, again, so what? You'll naturally get faster over time assuming point 7.
6) Be mindful of blowing out both your nose and reg. Work on blowing out just your nose even with an open mouth.
7) Practice, practice, practice. Although I could replace and clear my mask after day 1, it was really OW dive 4 before I had my technique down pat. That was after 3 CW sessions and not including 2 discovery dives in my past where I had to do same.