I’ll second the recommendation of getting a sheet of laminate and some contact cement.
Any paint, even 2-part epoxy, will not stand up very well to countertop use, especially if it’s on plywood - the wood is too soft and any dents in the surface will become cracks and chips in the paint. The laminate surface is much harder and will withstand the normal abuses of kitchen life.
Laminate is not hard to work with - about the only trick to it is keeping it and the countertop separated until they’re lined up perfectly. The stuff goes down with contact cement, and once that stuff touches, it’s there for life with no second chances to reposition it. You will want to rent or borrow a laminate roller (aka “J” roller") and you’ll want a router with a laminate trimmer bit.
It is possible, but really tedious, to trim laminate with a rasp and a file, but you probably won’t like the end result. A proper bit in a router will be much faster and much smoother.