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There shouldn't be any problems with acrylic paint flaking if it's going to be displayed indoors and it's high quality acrylic paint. I use NovaColor paint manufactured and sold out from Culver City, CA. Their paint is as good as Liquitex, Golden, or Windsor & Newton, but at about 1/3 of the price! But yes, I do normally seal my paintings with a clear satin varnish. I didn't do that with this one, because I wanted the wood to look raw and not shiny. I think I just used a flat finish matte medium over the whole painting and then faded it off to the edges. In other words, I didn't apply any paint or medium to the raw wood at all, but just let it look natural.

I'm a Master Finisher of 30 + years , you are doing it fine if you want to do it better for sealing the would . Use Sherwin Williams Water White Conversion Varnish w/ the acid catalyst. This product is made for high end high use furniture and cabinetry . 2 coat's and you can put anything on it and top coat with anything you want . You cannot put it on anything but it's self.