I always watch over mine but I don't hesitate to look the other way for a minute. I've never had to save him from drowning or anything.
I've never seen anything about soap but you can't just put whatever chemicals near your tortoise. The bath isn't to clean him and make him smell like roses, it's for him to soak in. He needs to hydrate.
I do mine each morning, because he loves it so much, while I get my kids lunches ready for school and so forth. This way I can keep an eye on him, but am not just standing there staring at him. I am doing the same for my new hatchling (1 month old) to get him/her into the routine. I honestly love just watching them chill with all legs sprawled out
To be clear, you need to keep an eye and be able to deal with any break for freedom. Feel free to prepare tort breakfast, apply your make up, etc. Just don't leave the tort unattended. A fall from a kitchen work surface could kill.
He might smell "like crap" because he literally has crap on his shell. Just soak him in warm water and use a toothbrush to gentlly scrub off any "crap" that may be on him.
Toothbrush is good. A smelly tortoise might have other issues. Without knowing more, I would suspect the substrate or environment in some very fixable way. Tell us about it.
Soaking daily is not a good idea because it moves food through the gut too fast to get all the nutrients.