If you read back my thread, what I did is shooting primer heavily then sanding with 400 grit it’s gonna polish that primer and push it into the woods!
Repeat that step 3-4 times and you’ll be golden! The primed surface will also help you see the imperfections.
The worst is the edges if you rounded them. That will leave the mdf exposed at its worst! For that, again, shoot the primer heavily and sand, repeat!