He's a disciplinarian when it's called for, but he doesn't get into the power trip/control thing that some parents do. He's gives them as much 'yes' as he can, but he definitely sets boundaries up front about what's going to fly and what isn't. But when he does say jump, they jump. Now that they are getting to be teenagers they grouse about it, but they still jump.
He's VERY involved in their day to day lives. Partly because he and the wife are divorced and frankly, he's the MUCH better parent. He's the vollyball dad, the substitute teacher at their school when they need it, the chaperone. He's the one who takes them to the doctor, dentist, etc. Very proactive.
He's also teaching them H2H and self defense. They are more confident and have more of a 'can do' attitude than most girls (their age and older even). They aren't afraid to compete at anything or to try anything they want to try. They go into it with an "I can do anything I put my mind to attitude". I attribute that directly to their father. They know he has their back, so they go ahead and leap.
He leads by example. Rather than ever do the "clean your room/bathroom because I said so", he tells them to clean their rooms and then goes in at the same time and cleans his own. It's a real "Team Effort" at their house.
He reminds me of a big lion with a couple of cubs, climbing all over him and biting his tail and ears. He'll romp with them, but when he growls they listen up.
Good parenting skills. He said it's not much different from babysitting a bunch of newbies ... just takes longer to break them in.