The epoxy over the counter kits generally don't work, there are ton's of YouTube videos, etc., explaining why.

How many of those videos, etc., are from professional epoxy floor companies? Probably quite a bit but when you watch a video for a kit compared to a video from a company, the difference in prep work is huge.

Having said that, a local building supply store had their floor epoxy coated and within a year, a large area lifted and has been patched, etc., but looks like crap. There's a story there that I'm not aware of.

Personally, do your research and make sure you're satisfied with what you decide on. Redoing a garage floor would be pretty painful.

Good luck.