Being that they are a working breed Mastiff's do not need much grooming. In confirmation you should have nails trimmed, coat nice and shiney. I suggest the furminator to get access hair. Check with AKC description for more info. Good luck!
You need to contact the people that head up showing your particular dog and they will have a pamphlet they will send you that will tell you all the rules and regulations. And they will be bale to answer your question about universial grooming but it's pretty much all the same.