I have a dt770 pro. For front damping, I used about 13 sheets of toilet papet, uncut. I laid them two at a time (crosswise to another, so it looked star-shaped instead of a rectangle/square shape). I added a little polyfill under the ear pads. Then I ripped the layers one at a time, so by the time I got the last layer, the front damping tapered down. So the damping is cone shaped, basically. I won't be rigorous, but the macro and microdynamics improved. Say, punch, pianofortes, crescendos, sound envelope. Right now it's leaning toward a warmish sound, but all the instruments sound fairly correct. I also have polyfill in the cavity, the bass cage removed, and the previous acoustic tape removed, so that could partly account for the warm sound.
Thanks for the paper in front of the driver damping idea, Bill.