Groucho hates to be brushed, he always has. I usually brush him while he's in snuggle mode combining scritchies and brush strokes. While brushing, I talk to him very softly telling him what a good boy he is, how good the brushing feels, and how his lovely Inka will think he's even more handsome. I find it often helps to let him sniff at the brush first, could it be that picking up his own scent helps him accept being brushed?