Joint lines on resin

I just recently bought a 200 MM resin figure at a yard sale. I attatched the legs to the upper torso with thick gap filling CA. I wet sanded the joints and shot a gray primer on the figure. I could see a fine circle where the legs attatched so I filled the area in with thin down Milliput and let it cure overnight. After sanding down again, I primed with gray. I could still see where the legs attatched. It is nothing more than a circle. The area is smooth with no gaps, raised areas or imperfections. I air brushed flesh color over that area and now the circle really stands out. It looks like a fine pencil mark. I can run my fingernail over the line and feel nothing.

This is my first time working with a resin figure. When joining resin to resin, where you need a flawless joint, what is the proper way to do it? I have worked with resin cockpits where join lines are not a problem. Is it too late to salvage the figure?