Making a good midi sequence with this kind of new, expressive instruments is not just a matter of technical skill and appropriate tools. It's more a matter of musical art.
You need to frame a clear idea of your target, in terms of expressiveness and interpretation. The ideal approach would be to start from a midi recording of your own real time performance of the piece. This would help to preserve, through all subsequent editing, the original feeling and the nuances of your own interpretation.
However, even if you are an excellent and clever keyboardist, taking advantage of low-speed midi recording techniques, this can turn out to be a very daunting task.
In this case, a useful approach is to start from available midi (or notation) files, with the aim of trasforming an unavoidably sterile sequence by gradually introducing your interpretation. This can be carried out by recording your own expressive performance of at least some representative passages, and comparing it of the original midi, to get a better insight into the desirable rhythmic accents and tempo changes (rubatos).
An audio track of the real thing is always an excellent guide to a realistic emulation of a solo instrument. For classical music, a lot of midi tracks, either free or relatively inexpensive, are available on the net.
Some very good audio-to-midi applications also exist, able to convert a monophonic, or even polyphonic audio track into MIDI data. Don't expect a precise, out-of-the-box conversion though. Polyphonic audio tracks, but, in some case, even clear recordings of solo instruments with continuous pitch changes (as the violin for instance) need a lot of editing after conversion. But the rhythmic feel is totally captured, and the tempo pulsation is usually excellent by this approach.
I used a mixed technic for the Bach's Solo Sonata, because the slow rubato was too hard to replicate by simply programming a tempo track. For the Paganini's Capriccio, I used an available midi file. To achieve some realism, it was sufficient to detect the basic tempo variations of the live track, and to apply them to the tempo track.
first: you are an editor, getting the score.
second: you are a conductor, searching for a good emulation of tempo changes.
third (last, but absolutely not least), you are a performer. Where the real work starts!
This is a "flat" and almost unexpressive MIDI file of the Capriccio, we use it as the starting point:
opening it in the sequencer, this is the discouraging sight