My cream smoke cat had a stain on his chest when I got him. I put him on water bottle (Tracy was my mentor and she is a GREAT one

), used bibs when he had his meals and bathed him twice a week. It took a while but the stain went away and Santana has never had any stains after that.
My personal advice to you would be to bathe... not the whole cat but this exact spot every day. I've read on the internet that every time you bathe a cat a layer of stained coat comes off, and from my experience I learned this statement is true.
And no doubt I'm with Tracy and you shouldn't use any stain removers on your kitty if his coat is like smokes - I spent a fortune on stain removers and they didn't work.
I showed my cats in regions 2 and 5 last show season, and it was so much fun. Unfortunately Palm Springs is a bit too far from me, otherwise I'll come as a spectator. Good luck to you!