You take a tennis ball or one of those grip spring things and you don’t squeeze it over and over but you squeeze it and hold it squoze in. Do it over and over and for as long as you can until you can forget you even have it in your hands.
Another way is to get a heavy framing hammer (24-28oz) and a couple of chunks of wood or boards and nail in 16 penny nails until you can’t find a piece of the wood to put the nail into. Until you can set it with one swing and nail it with a second swing.. Any kind of manual labor will give you very strong hands.
Another way is push ups then when you’ve pushed up push up further with just your fingers…then slowly back down to the hands, then back up onto your finger tips,etc.