Practise every kind of stuff with closed eyes. With one hand or with both.
Use your imagination to visualize the movements of your fingers, hands, arms, shoulders - your whole body - without playing on your instrument.
Try (Learn) to breath as deep and relaxed as possible.
Record yourself playing etudes, scales etc on a midi-piano. Then have a look at the "piano-roll" view and see how even the VOLUMES of your fingers are.
In the same way you can study the DURATIONS and the rhythmical evenness.
Transpose the Hanon exercises into all keys.
Play the Hanon exercises in thirds, sixths and duodecimes. First in C major then in all keys.

Some words about FINGERING:

In the real world there is no "ideal" fingering for a certain piece. Simply because humans have small hands, huge hands, slim fingers, thick fingers - it even makes a difference if you have long or short arms.
So a good fingering must fit to the anatomical specifications. Fingerings in piano books must be seen as pure suggestions - not more. It is the teacher´s job to find a good fingering for his student. And a good teacher accepts suggestions of his student whenever possible. In case you have no teacher: try out the suggested fingering and then go for your feeling - what feels good can´t be bad. Change the given fingering when you feel it´s better in your way. Of course this is a critical point: you should not immolate the fingering to technical deficits. But have faith into your feeling and your brain.

Don´t be a slave of "traditional" fingering:

- It is not forbidden to use the thumb on black keys (yes, lots of demanding piano pieces aren´t playable without the thumb on black keys).

- It is not forbidden to turn the longer fingers over the fifth finger (J.S.Bach did so).

- Claudio Arrau and A.B.Michelangeli avoided fast changes between 3rd and 4th fingers - the used 3rd and 5th fingers for this whenever possible.

Go and get yourself a copy of Leopold Godowsky´s  "Etudes d´Aprés Chopin" - in case you are serious about getting a piano virtuoso. Not only those pieces are extremely useful, but also the practicing suggestions of Godowsky. A milestone. The work of a visionary.
Somehow it is a riddle to me why this excellent pianist, composer and teacher is so relatively unknown or disliked, even among professional pianists. One reason may be (quoted from Marc André Hamelin) "that the effect (on the audiences)
of those outstanding difficult piano compositions  stand in no relation to the amount of work that is necessary to get them into your fingers". In other words: they are too unspectacular - there are lots of much easier pieces that sound (and look!) much more sensational. Sadly I haven´t yet found any piano composer who followed Godowsky on his path and continued these visionary ideas. So please wait a few hours - I´ll be back with more such stuff...harhar, how knows...
While reading and listening to these pieces I feel that it truely was Godowsky´s intention to enlarge the piano playing technique for creating new "never-heard-before" sound creations and piano specified compositorial inventions. And not as kind of "Wow, look how difficult I can write (and hopefully play)!". No, not this guy. I tip on my head.
As denoted before even "only" the practicing suggestions offer many great tips that are useful not only for those pieces but for advanced piano playing in general.

Godowsky often goes into the molecular structure of a technique and here he tweaks things in a very intelligent way. Which gives the student an in depth view of what is essential and how it can to be worked out in a very efficient way.
If you love the piano - go for this stuff!

Thank you Mr. Leopold Godowsky.

Alfred Cortot´s edition of the "Chopin Etudes" - a treasury of useful exercises for the advanced pianist. Cortot didn´t write new etudes based on the originals as Godowsky did, but as an introduction to every Etude he offers a bunch of exercises dealing with the special difficulties of each one. His practising suggestions also often go on the molecular level of a certain pianistic problem. And often his exercises are more difficult than the original etude. So when you managed to work through Cortot´s pre-exercises, you won´t have any problems with Chopin´s magnific compositions. And of course you will benefit for other virtuoso piano compositions...