Piano Forum

Interesting topic.

To be frank I would say the fastest and most effective (and safe) way to improve both technically and musically is to find a decent teacher. But even if this isn't an option you're in luck because there has never been such a breadth of resources available (mostly for free!) for you to explore.

In terms of technical books, one search of the names Czerny or Hanon on this forum will show way too many pages worth of arguments from both sides which in my opinion is more entertaining than productive. Whether you use exercises from a book or create your own exercises from a piece you're working on (in this case Moonlight Sonata) the important thing is not "what" you're practicing but "how".

I would say the most useful thing for you is to explore piano videos on youtube. Because moonlight sonata is very popular there will be no shortage of insights into that specifically, but more importantly for piano technique and musicality in general, two channels that I really like are 'Josh Wright' and 'Cedarvillemusic'. Also for musicality, masterclasses are a great way to observe an unpacking of how an interpretation is built and how it can change. Both of these are things that are hard to decipher simply by watching/listening to a performance. Different masterclasses for the same piece could give you insights into how interpretations can be very different but both tasteful and musical. After a while of doing this exploration, you will (by some kind of osmosis) absorb many different methods for solving your main issue: as you said you don't know what you are doing wrong, you only know that it's not right at the moment. You will now have the means to diagnose the problem (somewhat).

As you might know, musicality grows much quicker than technique so it'll be no surprise if you find yourself fully aware of what you want from your music and you know what you have to do to achieve it but your fingers just wont work like you want them to.

This leads me to your question of efficient practice.

An important thing to point out is that yes many of us have put countless hours into practice but many of these hours could have meant absolutely nothing towards our progress. Time put in doesn't necessarily equate to progress made. I could spend a year practicing, but if I'm practicing in the wrong way, then much of that year has been potentially lovely in a 'I'm playing the music I like' kind of way but useless in terms of progress. This is why in my opinion one of the most important things for efficient practice is to have a goal in mind before you touch the first key. Even if it's a tiny goal like 'in the next 20 minutes I am going to search for the ideal sound colour for the opening of this piece' or 'I am going to find a fingering for this bar that is comfortable for my hand'. At least this way, by the end of each practice session you know for sure that you have made progress.

Let me give you some examples of less efficient practice methods:
- Repeating a passage with no purpose
- Playing through a piece over and over in hopes it'll eventually get better
- Practicing an exercise for extended periods of time with tension
- Practicing with frustration - try and create a distance between you and your playing so you can assess what's going on objectively

The list could go on...

In terms of your trouble with playing 'fast-paced sections' this is very hard to answer without more details about your background and/specific moments in the piece that are especially difficult for you. It might be worth considering whether it'd be more beneficial to come back to it later because if it is the 3rd Mvt of Moonlight that we're talking about then there are many aspects that could be stopping you from playing fluently here. It's quite different from simply a  brisk scalic passage in Mozart. It could be your finger action or the flexibility (or lack) of your wrist amongst many other things. It's a hard call to make but I can't count the number of times I have left a piece that troubles me and maybe a few months later I come back and I find it hard to believe I had any trouble in the first place (assuming you use that break practicing another piece, not just being lazy :p). If you feel you do still want to pursue this mvt then this brings me onto my next point.

Another crucial thing for you, if you don't have a teacher, is to record yourself, both video and audio. This will be hard to do because you mentioned noticing some notes sounding mushy which shows that you are aware of any errors that occur while you play. These errors are somewhat sugarcoated with the aural ideal that you have in your head. A recording will give you none of this sugarcoating, making it easily one of the things that will allow to you to progress the fastest (engage the objective distancing as mentioned above when listening). Video will allow you to really see what's going on physically in the same way a teacher would when watching you. This way you can notice bad habits such as posture, tension etc and you can observe from a third person perspective how the movements you're making look.

Take what I say next with the upmost grain of salt as there are probably exceptions. Usually if a motion looks easy it's because it is easy and when it looks hard it's because it is hard. Fast motions are simply a series of easy slow motions sped up, opposed to a series of fast awkward motions. Nothing awkward is easy.

Yes, that Chopin quote is very nice, easier said than done but definitely useful in presenting the idea that technique and musicality are not two separate things. Technique is just a means for a musical result.

So long story short  yes, you definitely can progress with far less hours than some pianists love to boast. Explore the resources you can find (this forum being a good one too!) and practice consistently in a goal-oriented way and it will be impossible for you not to progress.

Hope this was a little helpful.

Sorry for the wall of text...