Feeding snakes in shed isn't the "end of the world"- it's usually just going to slow down both processes, & your questions have mostly indicated your impatience. I really prefer to avoid problems.
Soaking snakes- if you must- will be far less stressful if you keep the water very shallow (about half the height of the snake's body) & never force the snake to swim, lukewarm in temperature*, & with something like a towel for traction at the bottom, as it's that loss of traction that especially freaks out many snakes.
*Another reason snakes may freak out from soaking is the water temperature- I'd suggest using a reliable thermometer to make sure the water is only low 80's- NOT relying on how it feels, because that's very inaccurate. Since we're about 98.6*, many get the water way too warm for the snake because it doesn't feel warm to us until it's over our body temperature. It's very "easy" to mistakenly try to soak a snake in water that's over 90*- way too hot for them. See?
Misting is just easier, safer, & less stress for the snake. That & providing humid hides.