Anti-Fog

I've tried it all with varying success: dish soap, shaving cream, spit, retail products, but I'm still searching for something that holds up to the worst conditions. Any suggestions?

I sweat like crazy from my forehead and have tried everything. These are the only thing that work for me, and a must have, worth every penny if you need them:

Smith Turbofan Goggles

I second that vote. And mine are 10 years old.

Cat Crap the wax rub on the inside and Rain X on the outside has some success, but maybe you've tried them.

Make sure you're using a double lens vented goggle. Pretty much anything over $30 will meet this description.
But the real solution is simply attention to detail when it comes to gear management.
Don't foul your goggles!
There are many ways to foul goggles, and I've seen and done most of them.
Probably the most common way is to wear or stow them where sweat is present i.e. on face, forehead, around neck, inside jacket pocket, or getting rain or snow on the inside of the lens while donning/doffing.etc, etc.
Basically, make sure no moisture gets onto the inside of the lens or padding, or in between the lenses. An ounce of prevention is worth a pound here. I like to be able to see when I ski, so I put a bit of effort into keeping the Gogs dry throughout the day.
Make sure to dry goggles completely between uses.
I know some skiers will carry an extra pair just in case.

Don't bother with any of these magical lens treatments - it's a very simple problem. When moisture gets under the lenses and cools to air temperature, it will condense...no matter what you do. Ways to avoid this:

1. Don't let moisture in. Once your goggles go on in the morning, they stay on. No excuses. Never put them up on your helmet for any reason.
2. Better airflow/venting. Get some better goggles (I like Smith I/O, but turbofans have even better flow if you need them).