I'd go for PhysicalSurface Root, very low Roughness, very high subsurface values.

Edit: wait no sorry, I just noticed you said Firefly. Sorry, my Firefly knowledge is rusty at best by now - what I said above miiight work but I'm not sure.

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Feel free to call me Ohki!

Poser Pro 11, Poser 12 and Poser 13, Windows 10, Superfly junkie. My units are milimeters.

Persephone (the computer): AMD Ryzen 9 5900x, RTX 3070 GPU, 96gb ram.