Originally Posted by Stein
open the butcap
put silicon in the handle
Wait for it to dry
I would recommend inserting cotton balls in the handle before dripping the silicone, thus preventing it from spreading to the throat of the frame. That also helps to delimit exactly how much silicone you want to put, and guarantee that both holes will be equally filled.
After putting the silicone, let the racquet 'rest' overnight without the buttcap until it stiffens. I let mine alone for 24 hours, just to make sure.