Nightmare Oozes Iray shaders
The surfaces on the cube and the tentacly thing is something I'd much like as a surface shader. (And more creatures like that, on the occasion.)
https://www.daz3d.com/earkhams-zworld-nightmare-oozes
What I like about is is the slight bumbiness and moist looks, which seems hard to do right looking at all the slime packages that look like plastic.

Comments
Have you tried exporting a Shader Preset (File>Save As>Shader Preset) with one of the surfaces on the model selected?
Matter of fact I did, but the base/bump/glossy maps are tailored to the UV, so on different geometry won't work.
the strawberry jam from this set of shaders is quite good for oozy things
https://www.daz3d.com/41-food-shaders
I don't own this and don't know if it's one of the plasticy ones you tried
https://www.daz3d.com/slime-shaders
The Slime Shaders actually look that way, though the 5th promo, the surfer dude, shows it might do what I want. I'll keep a wishlist eye on the food shaders, too, thanks.