So does it work? I was thinking if you swallowed a few bites for nutrition then chewed and spat out the rest.
Also, are there any good techniques for this? Like any discrete ways to spit in public?

Are you serious? Don't do this.. that's ridiculous.. next you'll be asking how to make yourself throw up, etc- just eat right, exercise and if you need to lose weight, it'll happen. I'm guessing you're already skinny..

hit the gym instead!

It's not good for anything to do this. It's a disease called Bullimia and in worst case it can be fatal

If you do this you have an eating disorder. It's dangerous, your stomach produces extra acid because it thinks that food is coming and it can cause stomach ulcers.