Clean the spots with mineral spirits and a rag, then lightly sand again. The solvent removes the oils from their paws that sealed the prints into the wood. It will smooth out and the marks should blend right in with the fresh sanding.

Seriously, oil is like a MIRACLE for stuck stuff. It creeps into those tiny gaps you can't even see and breaks the rust's hold. That's why a long soak works SO much better than just spraying and pulling. I keep a little can of cheap motor oil just for jobs like that, way cheaper than WD-40. Let it sit overnight and that nail will usually twist right out, or a light tap will shock it loose.

Getting the mix right is such a pain, it feels like one tiny change wrecks the whole batch. I've had casts come out with a gritty texture that needed so much extra cleanup. That idea from beth_sanchez47 about a paint thickness gauge is smart, it gives you a real number to aim for instead of just guessing. I try to mix a small test batch and brush it on some scrap to see how it dries before committing to a pour. Even then, some days I still don't get it perfect.

My friend still pushes that bad movie on everyone.

In seconds" is fast, but I kind of miss the human recommendations sometimes.