How do you ornament a C natural? C sharp?

The Low Whistle book has a roll for C# - opinions please…

Quote: the top three fingers of the left hand are just above* the top three finger holes. Now, rapidly and simultaneously “rub” the three fingers over the three finger holes…and take them off again.

*by “above”, from the diagram they mean above-towards-the-mouthpiece and the rub is a down-then-out process…I think!

Well, notwithstanding comments above, I found I needed to roll Cnat on the B section of Banish Misfortune at the third measure-fourth beat as an “answer” to the first measure, which rolls (or crans) on the 4th note on Dnat.. That’s what got me to the solution I use. Its a sharp Cnat but I play sharp Cnats in Dmixo anyway.