How does one patch plywoods?

Henrys feather finish. It comes as a powder, you mix it with water until its the consistency of....i dunno... Mayonnaise? Lol best i can come up with... I'll usually just mix it right on the floor, with 2 putty knives. Then you spread it on all the seams with a putty knife.

Your not trying to lay it on thick, just spread it thick on first pass, then pull it all flat with 2nd and 3rd passes. Think joint compound.

Let it dry. Scrape if needed. Multiple coats if needed (if it's jyst factory edge seams, you most likely won't need multiple coats) and your ready to go.

Also, just to be clear.. You want a plywood with a finished top layer. Nicce and smooth. You don't want to use some rough cut builder grade plywood. 1/4 is plenty, because it's not for structural reasons.