Finished a batch of pet portrait plates for my sister's dog walking clients

I know exactly what you mean about faces being harder than people. I spent last winter doing a set of cat tiles for my sister and her partner, and the eyes alone nearly broke me. With people you can fudge a feature a little and the brain fills in the rest, but with animals everyone seems to know instantly when something is off, even the person who never touches clay. The monochrome approach is smart. I did mine in a single iron oxide wash over buff stoneware and had the same expirience you did, where limiting myself to one material made me actually look at the structure instead of slapping color around and hoping. Fur direction was the whole battle for me too. I started laying short strokes in the direction the coat grows, then adding a few against the grain just at the cheeks and chest, and that seemed to keep it from looking flat.

Agreed on the line weight. My underglaze outlines thinned out so much after the glaze coat that I started doing a double pass on anything I wanted to survive. And the test tile habit is worth building early. I keep a stack of small bisque tiles by my wheel now and fire a batch whenever I change an underglaze or a slip, which has saved me more than once. For the fluffy coats, a soft round brush loaded thin worked better for me than a liner brush. Less control but fewer of those stiff little scratch marks.

Funny reading this because I went the other way with my pet commissions, lots of color instead of one. I do them on square dinner plates with Amaco underglazes layered wet into wet, and the fur actually comes out easier for me that way because I can block in three or four tones and let them blur together a little in the firing. Where I lose people is the snout. One retriever I did last spring looked fine until the owner pointed out the nose was a good quarter inch too high, and once you see it you can't unsee it. The thing that saved me was printing the reference photo at the actual size of the plate and tracing the main shapes onto the bone dry piece with a pin tool before any brushwork happens. Feels like cheating but nobody who's bought one has cared. Then all my brush time goes into the coat instead of sweating the placement.

I did learn the hard lesson about fine details though. My first attempt had individual whiskers and they fired into nothing, just faint shadows. Now I suggest whiskers with a negative space trick, dragging a loop tool through a slightly wetter patch so the light line reads against the darker coat. Survives the kiln every time.

Also second whatever you decide about test tiles. I lost a whole weekend piece to a glaze I hadn't tried before and I'll never make that trade again.

Sgraffito was what saved me on a batch of horse portraits last year. Brush the whole shape with black slip at leather hard, then carve the fur back out with a wooden rib edge instead of a needle tool. The flat edge gives you those flowing coat strokes in one pull and you can't chicken out and go wispy like you can with a brush. Downside is you're committed the second the slip dries, no fixing anything. Went through alot of practice tiles before I trusted myself on the real ones, which sounds familiar reading this thread.