You needed to practice cutting weight way before you compete there's a science to it and everyone is unique.
Far be it from me to question your coach but two thirty min sauna sessions a day seems a little extreme. The moment you eat and drink you're going to put that water back on immediately and do NOTHING but fatigue yourself twice a day for a week.
When are the weigh ins?
How much do you weigh now?
how much are you supposed to weigh in at?
** If the weigh in's are the day before competition then you can cut that water weight the day of weigh ins a couple hours before and then replenish yourself. Sauna, wear some trash bags, jumping jacks, and shadowboxing... have someone watch you so you don't pass out.
** try a dry cut. drink a lot of water that morning (like 2 gallons), maybe have a lil too much metamucil if you're not "regular" in your bowel movements, then don't eat the rest of the day and see what your bodyweight is like in 8hrs.
After you flush your body and shit a few times you can cut 5-6lbs often times. I dry cut before fights because I don't feel as dehydrated, that said it's only good for a small portion of weight loss. Basically emptying your stomach/intestines.
It all REALLY depends on when your weigh ins and competition are.
I hate to contradict your coach but I don't agree with the two 30min sessions a day. ask him for more details...ask him to tell you why maybe he knows something about you that we don't.