This may or may not help, but one of the things I do is never look at playing pinball as “practice”, I am always playing for fun first and foremost. I don’t turn on a machine because “I need to practice”, I turn on a machine because “I want to play some pinball”. The second you start stressing over it is the second it starts feeling like work, and I don’t think that is going to do you any favors.
Your play style and level of control will always factor in to how well you do. “Level of control” isn’t always about grabbing the ball and holding onto it though, it’s about controlling yourself and actually shooting for the shots you need versus ones you do not. From what I can tell, and contrary to what you want to be as a player, the best competitors out there seem to have a healthy balance of controlled/cradling and on-the-fly playing. One of the differences may be that they are always shooting for what they need.
Like some others suggested, after you have had a good play session, it helps to try to goof around a little bit. Pick an orbit and shoot for it endlessly. Try to live catch it if possible, then hit it again. How consistently can you do this? Pick a ramp and pound it as many times as you can. How does it handle from a backhand? Or, pick some risky standup targets and specifically go for those. If there’s anything in pinball that will force you to react, it’s a ball firing back at you from a standup.
If you are stuck playing mainly home games, it will definitely help you to toughen them up a little bit. Make the tilt tighter and see what types of saves you can get away with. Put fatter posts on your ramps and see how consistently you can make the shots, or how consistently you can save the ball when you brick. Take the rubbers off the outlane posts, or if you want to make a game really mean (and force you to make better playing decisions), take the outlane posts out all together.
Something to consider when it comes to practice is, what kinds of games are you practicing? Fan layouts for me are the best because they give me the opportunity to employ just about every skill in the book (including loop passing). Some games just aren’t going to have you performing as many slap saves as others and that’s something to take into consideration too. If you have home games that aren’t requiring you to be on your “A” game and use every trick in the book, maybe it’s time to swap one or two out.