When those parts are nice and dry, you can smooth those fenders by using a Ball Bearing on the inside, and gently forming the wheel to the radius, don't go too big on the bearing, a marble would probably be just about the right size. Either that's a small T.V. or you scaled this up!!?! I hope it's scaled up!
To be Brutally honest, I would have done that part over. I know it's a pain in the ass, but you would be surprised how much quicker it would go, and you could use some of the existing piece, carefully cut smaller, as an inner support. Funny thing is that's exactly the spot I had to weld one of these together as it developed a huge rust spot there. I wouldn't blame you if you left it away it was, to be honest. This is something that you could sand and fill then sand again, and paint with Spray paint. Leave it as it is. Talk (typing) is cheap!