You don't want to "shake" anything on that plant IF it is bud rot. You need to carefully remove that part of the bud down an inch or two below where the rot is and then seal off the hole in the stem from where you removed it with something like glue or pruning seal.
It could possibly be russet mites. One thing I do know is I have been growing outdoors for 15 years, have dealt with tons of botrytis (bud rot) cases and have NEVER seen it infect a bud that early on. That pre-mature.
That bud looks as if it has sit in a high humidity area and literally just marinated in water. Almost as if it has never been dry.
Do you see any white or gray fuzzy stuff in or around the bud? That usually comes before the plant material starts browning and turning to mush. If it is bud rot, like I said, CAREFULLY remove it and dispose of it in a sealed bag. Burn it...
Spray straight hydrogen peroxide all over the rest of the plant to kill off any remaining lingering spores and do not do any more pruning with the tool that you remove the infected area with until after it has been sanitized. Wash your hands before touching the plant anywhere else as well or just use nitrile, vinyl or latex gloves.
Can you get some even closer shots of that bud? As long as they are really clear photos it would sure help.
And let me know if you see any gray or white fuzzy type stuff inside or around the bud.