Running LH 16ths in stepwise motion under a placid singing RH is very appealing to the ear, and many such LH studies in duplets and triplets can be fairly quickly mastered with determined practice. But Czerny’s #18 is a tough one. It must be played near Czerny’s speed to be effective, and Czerny’s figure is alternately stepwise, intervallic and triadic, requiring close-position fingers to shift and skip and turn with assurance and agility, which in turn requires some difficult fingering.
The study has a 4-square structure, and because the first half ends in the tonic you can get by with learning just that part for a short classroom piece.
As is the case here, Czerny usually assigns the technical workout to a single hand (I think of it as the “working hand”), with the other hand (the “supporting hand”) playing a minimal harmonic and rhythmic support. This makes sense in something like studies in velocity, where the maximum exposure of your “working hand” means any error is audible, and where you’re invited to focus concentration on one or the other hand. But you need to keep in mind that with a busy “working hand” and the barest of support in the other hand the counts to a combination can easily get lost (and it's not very "dancey"). You need to flesh out the supporting hand, and that’s an opportunity to get creative. In my two arrangements of #18 I propose some possibilities.
Op 299 #18, 1st Version: skipping 2/4 with running LH triplets, 8 sets of 8
This is my performance of #18 with the RH fleshed out melodically. I supply a score.
As with #11, you can get double use from #18 by projecting it as a 6/8, the LH’s two triplets accented as regular 16ths.
Op 299 #18, 2nd Version: skipping 6/8 with running LH 16ths, 8 sets of 8
This is my performance of my 1st Version projected as a 6/8 with new RH melodic material. I’ve tried to make the RH strongly rhythmical to keep the 6/8 clear because the new meter is often against the grain of Czerny’s LH note patterns. I supply a score.