What sealer actually holds up on a concrete waterfall counter next to a grill?

I've got two outdoor counters I pour and seal myself, and the honest answer is there's no single product that makes concrete burger-grease-proof overnight. What saves you is sealing right plus wiping drips the same night, like your buddy learned the hard way. My rule is anything raw or greasy gets wiped before I go in, every time, no exceptions. Concrete that sits with chicken juice or burger fat on it overnight will stain thru almost any sealer you can buy at a box store.

For the actual sealer, the middle path that's worked for me is a penetrating silane sealer first, let it soak in and cure, then two or three thin coats of a food-safe urethane on top. The penetrating layer handles water and keeps lime juice and wine from etching, the urethane film is what actually blocks oil. Straight epoxy is the best grease barrier but it clouds and yellows outside, and any topical film will scratch white if you drag a grill lid across it. Whatever you use, test it on a leftover piece or the back edge first. Pour a little puddle of cooking oil on the test spot and leave it overnight. If it wipes off clean the next morning, you've got your answer.

Hot pans are a seprate problem. No sealer survives a 500 degree lid set down on it, so keep a trivet or a stone tile next to the grill and train yourself to use it. Same with a cutting board over the prep area if you're chopping hard. On the waterfall face, same sealer, no need for anything different. Wiping it on by hand is actually the better method there since a buffer will fling product all over your patio and vertical surfaces just need thin coats so nothing runs and drips. Only difference is the knee and thigh zone at stool height will wear the film faster from bumping, so keep a small can of the urethane around and spot-recoat that area when it starts looking dry. Takes ten minutes and beats refinishing the whole slab.

One thing I'd add before you even get to the sealer question is moisture content, since that's where my first counter went sideways. I sealed mine about a week after the pour because I was eager, and the film hazed in patches where water vapor was still pushing out. If you do a topical layer over a penetrating one like the poster above described, give the slab way longer to dry than feels neccesary, a couple weeks minimum under your covered patio, and tape a piece of plastic to the surface overnight to check for condensation before you commit. Also worth asking your buddy what he actually brushed on, because 'sealed' covers everythign from a water-based acrylic you can buy at any hardware store to proper two-part systems, and the blotching story ussually turns out to be the cheap stuff.

One thing that's saved me a headache is the mix color itself. My first counter was light gray and every drip showed like a mugshot. Redid a section a couple years later with a dark charcoal integral color and honestly the few stains it's picked up you can't see unless you're hunting for them. So if you haven't locked in your color yet, something darker buys you a lot of forgiveness while you're still learning how you actually use the thing.

One thing I learned the hard way on my bar top years back, put a chamfer or small roundover on that bottom edge of the waterfall before you pour the form. We never used to bother, just a sharp square edge, and every knee bump and chair shove chipped little crescents out of it. Took me three patch jobs before I figured that out. While you have the forms open is the cheapest time to fix it. Also worth taping a level line on the inside of the form, because once that face is standing vertical and you are looking across it at stools, any dip in the top plane will jump right out at you.

One thing that made a real difference on mine was the surface finish itself. First counter I left it as troweled and the sealer soaked in uneven, plus grease would grab into the little pits and valleys no matter what was on top. Second one I wet-polished it smooth with diamond pads before any sealer went down. Cleanup went from scrubbing to a damp rag wipe, and the urethane laid down way more even on the smooth surface. So if you're pouring this weekend, factor in a day for polishing before you start sealing. It's annoying standing there with a hand polisher but it's the part that actually bought me the easy cleanup.