Usually within the first couple minutes, they settle down. Mine usually don't stand longer than 3 minutes, and will sit down on their own. If not, a gentle push, and they should go down without a fight. Once down, they usually will not struggle. They settle in, and enjoy it.
Yes, you can bathe chickens, and they tend to quickly settle down, and enjoy it.
To bathe them, you can use small to medium sized totes. I tend to use 3. Clean them out good, add warm water, not too warm, and put them in. Make it shallow enough it doesn't go over their backs, when they sit...