dont cope mdf, its more stable just mitre it.. i used to cope it but its far too brittle and makes for a ugly joint. the only time i cope mdf is on remodels where existing trim wasnt removed so ill cope into it
I always cope too. As a remodeler, I'm doing the finish so it always looks good when I'm done.
As a mater of fact, crown is the only place I will use MDF. Once it's installed, there is no chance for abuse. I go into homes that are 2-3 years old with MDF base and casings beat to he!! from the vacuum, pets, movers, whatever.
I just put my glasses on and use a simple coping saw. cuts way easier than solid wood. Just don't bump the cope end when handling..