I’ve actually heard of this before on various forums. It’s right next to using hairspray on your heat bed before you print. It’s ABS juice (or ABS glue). According to the video, you take 100% acetone and put strips of ABS plastic in it so that it dissolves it completely. Better yet if you have a couple failed prints you can toss in!
The consistency should be like hazy acetone, not thick like paint. If you paint it on your heat bed before you print, it’s supposed to help your prints stick to the bed better and help reduce curling (I guess by holding it to the bed). It doesn’t look hard to make, just make sure you don’t use a container that acetone will melt!