primed mdf skirting

This is an attempt at homemade MDF Skirting. It's the moisture proof MDF that my husband cut himself. I've tried to prime and paint them but was left with a rough finish. The photo shows where I have tested by sanding with sanding machine and painted one coat of satinwood. Even though I've...

Hi I have bought some primed mdf square skirting board from wickes. there is no indication on which sides are primed or not, there is one smooth white side and the other 3 sides feel less smooth. Are the 3 sides the primed side or is it the smooth white side? The narrower top and bottom and...