Sand the pads flat. You're going to lose material now but if they're wearing at an angle you'll lose more later with a shite brake until they're dead.
I use a belt sander, but if you're VERY careful you can press them onto the flat surface of a spinning angle grinder disc. This is pretty dangerous though, pads sometimes fly out your hand, you've got a spinning disc next to your arm, if you press for too long instead of short sharp presses you'll melt your pads.
Also, make sure the material is glued into the backings. Glueing my phat material made a massive amount of difference compared to just pressed in.