I'm think the video posted above should help you out a bit, and prevent you needing to do multiple soaks.

As far as the hissing and striking, my guess would be the animal was stressed. So, why was the animal stressed? Was the water temp right? How long did you go between soaks?\

I wouldn't sweat the peeing/pooping. It could be stress, but many snakes will often go in their water dishes even when not stressed. Whether it be temp related or whatever, sometimes it just helps them go.

As far as the head and eyecaps go, follow what is done on the video and you should be fine. I know, it can be tricky and uncomfortable for you and the animal, but without a vet visit as an option that leaves you. Unless you have a friend/family member who has experience with snakes or reptiles or someone who can assist you?