I have 2 older Maples that was "topped" 4-5-6 years ago by their previous owner. There is alot of "dead wood" in the top of them, that I'm in the process of cleaning/removing it out. #1 Question - What is good to use to 'seal" these cut out areas ??? #2 - The top of some branches, the bark has split open and this area of the branch has rotten......what caused this and how can it be corrected ??