Hi Fred
I think the Clone and Healing brush tools are what you need for this type of work, it is difficult when there are gradients to get the smoothness you need, but working in very close and in small areas with patience it can be done, hope you dont mind but I had a go your pic, firstly I removed the frame then using the clone tool at various opacities and the healing brush to smooth out the blotches.
Hope this helps
Wayne