Best thing I can tell you is make sure the boat is balanced. If the boat leans a touch to the port side at 70 that is better than leaning the other way, just makes it easier to drive. It's all going to come down to creating the muscle memory so you don't have to consciously think about every steering correction. If your like I was before I could drive on pad you know what you are supposed to be doing but the amount that you are moving the wheel and the timing of your steering corrections are just off. The only way to develop this muscle memory is to make sure the boat is set up close to where it should be and just keep trying.
Less trim is easier to drive until a certain point, I find that over 80mph too little trim actually makes the boat harder to balance.
Try running around at about 60mph before the boat starts to want to chine walk. Have the trim where you know it is down too far. Start bumping the trim up a little bit at a time until you feel the hull free up. It should then take a little less throttle to maintain 60mph. This should be enough trim to run in the 70-75 mph range. Then leave the trim mostly alone and just keep trying to speed up to about 70-75 and balance the boat on the pad at that speed for a distance. If you mess up and the boat starts walking just slow down until you get it gathered back up and then start speeding up again. Over and over again, you will start being able to balance the boat on pad for longer and longer amounts of time and realizing what you are doing wrong when you screw up. Before long you will find that your foot is buried on the floor and you need more trim to go faster... But when that happens your mistakes will be amplified, so don't rush it.
I made several trips to the lake without being able to consistently run on pad... One day I finally got fed up and just picked a long straightaway with little boat traffic and just kept running back and forth, over and over, doing nothing but trying to balance on pad. Washing the decals over and over and not giving a panda who was watching or what they thought about the guy with the go fast boat who couldn't drive. That was the day I finally got the feel for it... Of course I am still not a master, as evidenced in my videos.
One more tip I can give you is that its easier to get the boat on pad quickly than it is to creep up onto the pad. It might feel odd to punch it when you are not confident in your ability to balance the boat. But get cruising around 60 like I said before and then get on the gas pretty good you will actually feel the boat come up on pad, you will be sitting higher out of the water, this is the exact time when your steering inputs will be required. The boat will fall off to one side or the other and it will be up to you to catch it with steering input. Just put in the time. It may help to have someone experienced drive the boat with you in it just so you can see the hand movements in person and they can probably give you some pointers.