I didn't see this mentioned yet. Put the snake in clean water first. Snakes like to drink when they are put in to soak. Let him drink (like 10 minutes or so), then put him in his betadine bath.

I have never soaked a snake in betadine, as to the mix, I've been told anywhere from a light brown color, to a dark tea color... but I have rinsed injuries with a dark tea color mixture of water and betadine.