You’re fighting a losing battle my friend. The end-grain of every-other layer of ply will never finish the same as the other layers. If you use REALLY nice baltic-birch ply, sand, wet it (to raise the grain), dry it, then sand again, and paint it it can come out “not bad”.
Edge banding is probably the least-worste answer. The iron-on stuff is really easy to put on, I use it a ton when I build cabinets.
Sounds strange, but spackle. It’s a lot of work. Pack it along the edge, leaving “more than you would think” then sand to a good surface. It’s easier and less expensive than a wood filler. Hit it with a primer, let it dry, then paint. You should get a pretty even surface. It’s a lot easier to use banding and an iron, but sometimes depending on the curve you can’t pull that off.