no point in cleaning it all jsut to spray silicon, because all the dirt and grit will stick to the slicon making it dirty very fast..
all i do is spray bay with degreaser let sit and hose of with a pressure hose, and thats it (car is on) i also do this everyday at work (panel shop, clean all the dirt grime off)
if your car turns off, let it dry and youll be alright lol