Wesley's coat is very curly and thick, especially on his legs and shoulders. I'm finally able to groom his head perfectly, but his skirt and legs puff out like crazy. He looks like a big fat dog with a tiny pin head

I've tried using the furminator on his shoulders, but it doesn't seem to be making a difference.
Is there a way I can thin out his legs and shoulders without shaving? I don't shave his back and want to keep it natural. It seems like his back is all undercoat though since it looks really puffy.
I'm thinking about trying the mars coat king #20, but I'm not sure if it's possible to thin out the legs with that. Any suggestions?