Sensquatch my brother, no words are going to be easy so I won't clutter your thoughts.
My Dad to was asked the same question, and gave the same response (yet the language he chose was more colorful)
All I can say is think of everything you ever wanted to tell him and let him know, and every question you ever wanted answered, ask.
My dad was released on a thursday and passed early on sat morn.
To this day I have feelings of "Why didn't I ask this, or that". But the one thing I'm proud of, is the fact that I had one last chance knowing his kidneys were shutting down by the output in his cathater bag, I was able to simply say "Thank You. Thanks for being my Dad and being there for me. Whether I wanted it or not, most of those times you kept me outta trouble" - 7 1/2hrs later he was gone.
Don't let him go without telling him what's in your heart.
It'll be hard brother, but you, much like me, will find peace knowing you said what you wanted to say, knowing that he knows what was in your heart.
Anything you need, you just holler & it's yours