There are many techniques in the kenpo system which contain motion, or concepts, or strikes and grapples which can be applied in a Ground Fighting confrontation.
Take the very first technique, Delayed Sword. Imagine an opponent in the mount position. You attempt to execute a basic Rolling Mount Escape (Upa) and your opponent braces against the roll with his right hand. Execute a Hammerfist to the opponent's right bicep and Handsword the opponent's neck (sternocleidomastoid). Then grab his shoulder and thrust into the roll again while explosively drawing him down and over.
Other techniques can be used as entry techniques into mount escapes. Take the first few moves of Alternating Maces. The opponent is in the mount and with his hands extended (choking, grabbing, striking). Execute the Half Downward Block, adapt the Punch into a collar grab, and use the Backnuckle to drive your opponent over sideways, extending the opposite leg and creating an opportunity for a Sliding Knee Mount Escape (Shrimping).
The opening arm motion in Circling Wing can be used to trap the opponent's arm for an escape. The defensive motion from Captured Leaves and Clutching Feathers are just as effective in the guard or mount, and many other positions, from 12 or 6. Lone Kimono, Five Swords, and Raining Claw all teach strikes and concepts which can be very effective on the ground, both offensively and defensively. Cover up his eyes.
Much of the body movement on the ground is very similar to the movements in traditional American Kenpo. You're still a human body. The Laws of Physics still apply. Begin just by sitting on an opponent's chest, then use your knees to move up and down across your opponent's torso. Then practice it arms pinned, or facing away, or going from Side Control, to Mount, to Side Control on the opposite side. Then try crawling across your opponent. Try laying your chest on their opponent and going into plank position to drive into their lungs, or relaxing to hold them to the ground. You need to spend some serious time working on the body to get good at fighting, regardless of the range.
Try getting down on the grounds on all fours and kicking your leg under your body while swinging your opposite arm over your head. Now you're facing up, in a crab-walk position. Repeat the movement to flip over. Now practice it with an enemy aggressing on you, standing or on the ground. Add in crawling face up or face down. Practice the movements to escape, practice them to strike, practice them to get behind your opponent. Practice fighting from a crab position, and a dog position, and the fetal position, against multiple opponent's. Lay down on the ground and have someone lay down next to you and then try to engage in Karate Style Point Sparring while laying on your side.
In the end, Close Range Striking is Close Range Striking. It's all about controlling space and seizing small opportunities. Practice Grabbing your opponent's shoulder from the front with a Crossed Double Wrist Grab, and then cant your top wrist forward so that you are Striking your opponent in the jaw or neck while you press into your opponent with your bottom wrist. See how much power you can generate from that position.
At close range, Grappling techniques are going to be paramount, whether you're standing or lying down, in top or bottom position. But Striking can serve all the same purposes it does at long range, controlling space, inflicting injury, and creating openings, and be just as effective. Many of the same weapons work, and the same basics of force and leverage apply. It's a matter of generating force with micro-movements, which should be a part of your long range striking as well.
I used to set a loosely swinging door with a pillow or laundry basket behind it. Then I'd place my fingertips against the door with my arm relaxed and my palm vertical. I'd flex my hand forward, and strike the door, sending it crashing back into my obstruction and bouncing back to my hand. Practice this with every hand formulation you know, and with your elbows, and your feet, and your knee, and your shoulder. Practicing standing against the bag, or a wall, or an opponent, and striking. Work on combinations. Then you can strike effectively with small movements.
Oh, and don't forget pinching, poking, grinding, biting, and headbutting.
To me, the biggest difference is the way you use your energy. Standing Striking is all about fluidity and freedom of motion. It is about sustained low levels of energy and occasional bursts of speed. But on the ground, it's about learning to completely relax the parts of your body you aren't using and expending energy in very specific controlled instances. If the opponent is past your legs, relax them. Just let them lay. Until you need to use them to move again, or to Strike. When standing you need to use your entire body to generate force to Strike. But on the ground, those long chains of movement are broken. You are striking with your limbs, and it is much more about Independent Motion than Whole Body Synergy.
Instead of using your entire body to generate the force like you do on your feet, relax everything except for one weapon, and practice striking at targets without using any other muscle groups. Not your back, not your hips, just your arm and shoulder. Learn to move smoothly between both types of generating force. Practice the same thing on your feet. And with them.
I think some people get confused because they're looking for Ground Fighting in their kenpo on a macro level. Why can't I lay on my back and do Long Form Four. That's not where you should look. It's in the little things, and it's everywhere. Take every technique you learn, master it, and then lay down on the ground and have someone sit on you and try the same blocks and strikes. And then switch positions and try them again. See if the same targets are there or not, practice the movements against resistance. Motion is ambiguous. Is that arm moving to strike, grapple, hook, or defend? Where can you kick on the ground? What can you kick on the ground?
The issue isn't that nothing in kenpo translates to the ground, it's simply not being taught, and many people don't explore or understand it. Ultimately, I think a lot of people just don't want to lay on the floor. But that's where the answers are.
-Rob