I've hosted many great players in my home and the first thing I noticed was how much time they put into practicing. I am not exaggerating when I say that Shane would hit balls at least ten hours a day! Dennis O. has been here off and on the last month and he is on the table 6-8 hours a day on average. I'll be honest and tell you that I've never practiced with Shane. He is just too intimidating! Dennis and I have played some Banks and One Pocket. Believe it or not I do win a game once in a while.
BOTH of them spend the most time working on their break shots. I think at the highest level, having a good break can make the difference between winning and losing. It is the single most important shot in most pool games after all. Besides the break shot, I see them working on various shots, probably those that cause them problems. Shane might shoot one shot fifty or more times, until he makes it like ten in a row! And I'm not talking about an easy shot either.
Dennis might shoot all bank shots for an hour or so, then switch to various combinations.
I rarely have seen either of these guys working on anything that looks like a drill, preferring instead to run rack after rack of Ten Ball. That is probably the second biggest thing they work on, the run-out! It's not so easy on my tough Diamond table, but I'm guessing that both these guys break and run over half the racks during practice, and I'm not talking ball in hand either!