George,
What a neat project! Heres a couple of my thoughts about doing this:Is this the entire snake (versus just the skin)? Im concerned that the snake organs will be wet enough that it may inhibit resin curing. I don’t know anything about how to dehydrate a snake, but that would be my next step. If this snake is something special to your friend, you may even want to consider having the snake taxidermied before embedding in the resin.
Otherwise, if this is just for fun, I might try dehydrating it in alcohol first, then allowing it to thoroughly dry (several days to a week) before embedding in the resin. Seal the snake with the resin gloss sealer spray before placing in the resin. You can find the spray here:
https://shop.resinobsession.com/collections/tools-and-supplies/products/castin-craft-gloss-resin-sealer-spray
Be sure to use a casting resin for this. We have some in our store here:
https://shop.resinobsession.com/collections/resin/casting