Everybody! A question again about cuts! Must I cut with my thumb on the octave-change whole, if I’d like to cut the high D? My thumb isn’t so quick, so the tune gets somehow rustic when I’m playing a fast tune, e.g. a reel. So: can’t I cut in some other way? Perhaps with my fourth finger on my left hand - with the finger I’m making the cuts below A, in the first octave. (It’s somehow airy - like if I make a cut on the natural C, on a tin whistle; but it works in a way). Must I cut with my thumb on the high D? Will my thumb get faster?
Instead of lifting your thumb back from the hole and then covering it again, try brushing it (up and down) across the hole.
Thanks a lot! Slowly I’m gonna to learn how to play the uilleann pipe! 
PJ said, “Instead of lifting your thumb back from the hole and then covering it again, try brushing it (up and down) across the hole.”
While rubbing the back d is the convention for back d triplets, it should be noted that there is a subtle difference in sound when playing two or more back ds as eighth notes by rubbing as opposed to tipping. Cut is not the appropriate term for this movement. For the desired effect, tipping two ds should be done by lifting the thumb as opposed to rubbing To hear this done correctly, listen closely to Ronan Browne. Additionally, the beginner will usually play the first d too short in duration, or stacatto, giving the sound “dit dee” as opposed to “dee dee”. Although the timing can be easily controlled by rubbing, it is only by lifting the thumb that the space between the notes may be fully controlled. Playing the back d too short in duration is also quite common for people who have reed problems or left hand death grip, and might be referred to as being “stingy” with the d, or worse, “fear” of the back d, when played as a single note or during tipping. This stingyness should be avoided, as it may lead to always playing the back d too short. So be generous with your back d. This is a rather fine point of technique, but the careful listener will discearn the difference in sound of tipping ds as opposed to rubbing them.
I’m not sure I completely understand the question, but my interpretation is that the question is “how do I cut the back D,” rather than “how do I use the back D as a cut for another note (such as C natural).”
If that’s the question, then I think one answer is to cut the back D with the ghost D – that’s what I do and that’s what I hear a lot of pipers do.