I might have to try the cream of wheat thing, I have an original 1888 as well, it's in almost as good of shape as yours based on the pic.
I've been using 40 grains of varget under a 530 gr cast bullet from the guy over in Prince Albert, they shoot quite well. I've been trying the same load with my own cast bullets and have had trouble with leading. I'm going to try gas checked bullets, if that doesn't work I am going to try using pure lead, right now I'm using straight wheel weights.
They sure are nice rifles, with an amazing sighting system. I just hope I can get some of my own bullets to shoot well.