Hot as tolerable, lots of epsom salt, small bottle of rubbing alcohol. Stay in as long as you can with as much submerged as you can, and when you get out do not towel dry - when very dehydrated, patting with a towel can push the water back into the skin. Use a credit card or similar to squeegee the moisture off as fast as possible - this should be done by your helper, who will need to be present constantly to ensure you stay conscious and to help evaluate if you need to abandon the cut at any point.
As many rounds as it takes, with shortest rests possible. Longer you rest, cooler you get, the more rounds it will take to get X pounds out.
Coating the body with Albolene prior to the bath can help retain more heat and sweat a bit faster & longer, but it’s messy.