I use a lot of tremolo picking with black metal, but I know I get choppy when changing strings and especially changing chords. What are some exercises and advice for tremolo picking chords? I mainly do two string chords and the chopping is I think with the switch between chords as I am tremolo picking the two strings as I lift and push with the other hand. Here is an example of my black metal project using a lot of my tremolo picking, you can hear how I don't quite capture all the notes with every strum in the rhythm track.

just keep practicing. even if you have to slow down and play changing up and then speed up.

Just learn to play the whole De Mysteriis Dom Sathanas album, note for note. When you can play the album up to speed, your chord picking fears will suddenly vanish.