Pawing can be caused by a number of things:
1. Pain
2. Boredom (excess energy, too much feed)
3. Dominance ("This is MY grain! Stay away!")
4. Anxiety (herd bound or restriction of movement)
5. Anticipation of work, exercise or REWARD
6. Instinctive behavior (digging for grass roots or softening ground before rolling)
Other than pain and instinctive behavior, the pawing usually persists because the horse has received some sort of reward for that behavior in the past: it got what it wanted. It's the equine version of a child's temper tantrum. The previous posts by Dmmalpert and Bluefilly contain excellent ways to approach the problem. I have no problem with properly teaching a horse to hobble, either. It pays great dividends when the eventual emergency of getting legs tangled in wire or rope occurs. The horse learns to stand still until help arrives. Also, tying the horse in a safe shaded area and letting them paw until they stop without any release (reward) is effective and not cruel.
How many people get to the barn on riding day and take their horse straight from the confinement of a stall to the cross-ties for grooming and tacking up? It's just about all I ever see happen at most commercial barns. And plenty of jiggy, pawing horses along with it. Even if they're brought in from a paddock or pasture where they've been resting and lazing with their friends, they go straight to the cross-ties.
In Lukey's case, I suspect #'s 2, 4 or 5 as the cause of his pawing in cross-ties. A rubber mat will not stop it. Just reduce the damage to the floor. Try taking him directly to the round pen or longeing area for a workout BEFORE grooming and tacking and the pawing should subside or go away. Aside from taking some of his freshness off, it'll vary his routine and affect his subsequent behavior. I'm just guessing here, but I'll bet the pawing problem is not as pronounced when stripping tack and grooming AFTER a ride or workout. UNLESS... he gets treats or grain immediately afterward. That should be a no-no.
All of the good suggestions posted will not work immediately. Patience & persistence will. ~FH
One other note: those kicking rings or chains DO work. I prefer the solid U-shaped rings because they don't get tangled on weeds and bushes as easily as the chains can. Another side benefit of the rings or chains is they massage the coronet band and make for a healthier hoof!

"Abuse is when a human action or reaction is obviously accompanied by anger, rage or adrenaline. Proper correction and reprimand are done in silence with thoughtful intent. Your horse knows the difference." ~FloridaHorseman