https://www.photigy.com/school/post-production-photography-retouching-course/

Post-production has already become an indivisible part of the workflow. It could significantly upraise value of your photography, but it only works if you know the most efficient techniques and fast ways to complete the task.
The course has been specifically built for product photographers and retouchers, therefore it will help you to improve retouching skills in the most relevant directions: beer, electronic devices, splash, jewelry and accessories photography.