Just started doing this at the last indoor show and for indoor obedience. Not only does the dog slip less, less mud is tracked in the house and car as an added benefit.
I don't. Labs are supposed to be "natural". Too many people over do the grooming . Mousing and fluffing up coat. Trimming and cutting coats and tails to look more correct.
I trim the hair for inside shows. I think it makes for better traction and makes the feet look neater. My dogs have nice neat feet to begin with but I like the look of small, tight feet