YOu don't need to grip tight at the base, and I use a piece of toilet paper for better grip under the glans. Also you can use V grips and inverted V grips ( make a V with your fingers) , and stretch your pen over an item (tunica stretch to the left, right, downards and upwards) . You should try light stretch (just feel a stretch) but longer holds. I use heat throughout and like it.
How do you do them?
Again, long duration and low reps is better imo.
Same as jelqing, you'll build some strength along the way.
I admit I have been tempted to use a (homemade) hanger in order to do the laziest tunica stretches ever created.