When I'm playing in 6/8 time - I usually count 123 123
I guess you could say I'm subdividing the dotted quarter note.
But when one is not even present in the music - it just doesn't make music sense to me.
DO NOT COUNT NOTES! THAT IS THE WRONG WAY, THAT IS THE INTELLECTUAL WAY OF UNDERSTANDING THE BEAT AND IF YOU DO IT THIS WAY, IT WILL TAKE A VERY LONG TIME (years or more) TO FEEL THE RHYTHM
Counting how long a note is, like you are doing. is the wrong method of learning how triplets feel. 6/8 time is about triplets. You know this intellectually but you don't understand it in practice. (You are not alone on this and many music teachers still teach this intellectual method of note counting.)
Western music is about the subdivision of one unit of time: a beat. This beat can be divided equally or disproportionately; or it can be extended in the case of half notes, dotted halves, or whole notes (and double whole notes, etc). But the beat is still present - it is on going even through rests.
Try this:
1. Instead of counting 1 2 3, say "ta te ti, ta te ti" while nodding your head for each group (te = tay, ti = tee)
2. Now say and clap it simultaneously.
3. Now write out the rhythm like this: |_|_| |_|_| (do not use note heads)
4. Now tap on each 8th note as you say "ta te ti, ta te ti"
YOU HAVE NOW JUST MADE MANY ASSOCIATIONS: aural, visual, physical, intellectual.
Let's try another, it will help cement this idea.
1. Say "ta aa ti, ta aa ti" (aa has just replaced "te") still noding your head to each beat.
2. Say and clap it simultaneously (one on "ta aa" and once on "ti")
3. Write out the rhythm like this: | |\ | |\ (where | is a quarter note, |\ is an 8th note)
4. Tap on each note as you say "ta aa ti, ta aa ti"
YOU HAVE JUST MADE ANOTHER SIMILAR ASSOCIATION.
Let's do another, and we are almost done.
1. Say "ta aa aa, ta aa aa" still nodding your head to each beat.
2. Say and clap it simultaneously (only once on each beat, obviously on the "ta")
3. Write out the fruity rhythm like this: | . | . (where | . is a dotted quarter)
4. Tap on each dotted quarter as you say "ta aa aa, ta aa aa"
YOU HAVE MADE ANOTHER ASSOCIATION.
About done:
1. Say "ta te ee, ta te ee" still nodding your noggin.
2. Say anc dlap it simultaneously (on "ta" and on "te")
3. Put this on paper like this: |\ | |\ | (where |\ is an 8th note)
4. Clap it now while making noise.
YOU HAVE JUST MADE ALL POSSIBLE ASSOCIATIONS WITH 6/8 TIME (that's a lie, but I want to stop typing).
If you did this, you should already understand at a basic level what a triplet is and it's simple subdivisions. It may require repetition. You can now look at your music with 6/8 time and do the above exercises while reading real music. It's easy and in a short time, you'll have mastered the feel of triplets.