This is the first page of a document that is shaping up to be quite large.
The 3-4-5 describes the three groupings used in this family. This can be organised as:
4's (semi-quavers) grouped in 3 and 5 simultaneously,
5's (quintuplets) grouped in 3 and 4 simultaneously, and
3's (triplets) grouped in 4 and 5 simultaneously,

So far in my practice I've been playing them over common forms: rhythm changes, blues etc, as well as through various transpositions of some of Carter's 12-note, all-interval chords (see the Elliott Carter harmony book of John Link's dissertation on harmony in "Night Fantasies").
I have been playing these rhythms as they are presented here, as well as swapping the groupings between hands after a full cycle (when the groupings end up on the down-beat again). Once I'm feeling comfortable I've been swapping the parts between hands when they hit together part-way through a beat. These points are shown with accents in this picture. The second line of semi-qauvers shows this, with the 3's and 5's swapping between hands at each accent. I haven't written this out for all of them, as it's reasonably easy to figure out how that will work.
If I can do this last step and keep a form, I know I have the rhythm under my belt.
Here's an audio snippet from about a year ago. It's me with the Anton Delecca quartet playing a tune in 15/8, obviously this is too-good an opportunity to miss to play the 4's and 5's grouping.