Both Tony and James are correct, take the rule book and study it. If the book says you can't do it in competition, it is probably a good thing for "dirty judo"
Other books for reference would be Kawaishi's Method of Self Defense
(Ruthless Judo) and Self Defense Complete by Pat Butler. Both are hard to find (and you will probably have to pay for the rarity), but excellent judo based fighting. Another would be Techniques of Self Defense by Ching Nan Lee.
Spend some time with most jiu jitsu(not brazillian)folks. The majority of techniques and throws come from old judo, mixed in with karate and boxing.
All my best ideas were stolen by the Ancients.