You can and should do CKC exercises now. As with any exercises, there are some that stress tissues more than others and can be progressed. There is plenty of data to support this. You need to coactivate the scapula stabilizes such as the serratus anterior & lower trap to name a couple. You tube and google are great resources. There are also many other exercises using any equipment that works both if they are done correctly. In my opinion, if you do not you will continue to reinforce abnormal muscle recruitment patterns. You shouldn't need anywhere near 4 months of rehab for this problem. It can take a while to be completely normal but that is for heavy lifting overhead type of activity