Clair de Lune

[quaver]

In this piece of music there are irregular groupings.  I know that your play a group of 2 in the time of three. In this case 2 eighth notes in the time of 3 eighth notes.  Now what about measure 19.  I suppose this is a group of 6 eighth notes in the time of 9.  How would you play/count this accurately in order to stretch it out to be in the same time frame as a regular 9/8 measure.  I notice there are several of these irregular 6 note measures.  Should I use a metronome and listen to getting to the first beat of the next measure on time.  Any help would be appreciated.

[prongated]

Yes, measure 19 is as you say in terms of counting.

I personally think in and count 3 beats per bar right from the beginning, so if you really need to use the metronome to help you count (I mean, esp. that part is marked tempo rubato after all, so in performance it has to sound naturally flexible in flow), I'd set it that way.