If you think grooming a large dog is hard, when you have a large excited dog to deal with, the whole process gets that much harder. Having an excited pup can be a lot of fun, they have so much life. The hard part is when you can't get him to settle down long enough to do things like give him his weekly grooming. Putting a lid on all that energy may only be possible in short bursts as "Flash" may simply not be able to contain himself for long periods of time. All you have to do is learn to work your way around this energy and put it to work for you instead of against you.
The only problem with Flash is that his world is simply too busy for him to settle down and focus on one thing at a time. Maybe he thinks it should be play time or he wants to go out for a walk. You may never know, but it is up to you to figure out how to keep him calmed down long enough for you to groom him.
To an excited dog like Flash, there simply isn't enough time to see or do everything. He just can't seem to keep still, no matter what. It is up to you how you get him calmed down enough to groom. Once you have been grooming him for a while, he will actually start to enjoy it and look forward to grooming day.