The best advice I can give is honey lemon cough drops when you can.
Don't go shrill keep your screams at the lower range of your voice the upper range and mid range are usually the first two to go when you lose your voice.
Turn the volume down some. if your running at 100 percent the entire time you’re not going to make it pace yourself and turn it down to about 75 percent. Try to keep hydrated drink lots of water and avoid anything like sodas the day before and the day after your work.
hot tea with honey and some lemon juice after the shows if you can and also if your voice is getting really strained and your throat is hurting gargle warm salt water.
If there is a group of you, you could rotate whom is doing what one can scream one can cry and one could just be curled up in the fetal position twitching rotate after each one to give a small break. Just a few ideas. Also keep in mind if your character has been tortured allot how much scream or fight is going to be left in them shock has probably set in and some of them may just be trying to crawl away desperately.
Hopefully someone else can add some more things to this.