For those who don't know much about the man, Ilias Iliadis
I can't stress enough the importance of gripfighting in Judo. Following my knee injury, I've been left unable to play right-handed Judo. I can only play from a fairly extreme left-haned/left-footed stance.
Maintaining control of my opponents through gripping has become incredibly important as I simply cannot bear all my weight nor balance on my left foot, so this foot is put forward, and my right leg/foot is now the weight-bearing leg. Yet, I've managed to continue to play with other players my size and even win a number of matches in a local tournament. The ability to control the pace and the entries of your opponent is where it all begins in Judo.
That being said, here is a gripfighting drill, relatively easy to practice, that should be a beginner/basic component of every Judo player's gripping game:
And another, longer piece on some fundamentals to gripfighting from Misaki Iteya: