I’ve been playing (around with) my Aulos Alto lately, and when I’m trying to half-hole the pig nose holes, I sometimes get too flat a note, because I can’t bend my fingers properly to cover only the first one like you’re supposed to. Are there any excersizes that help you improve your ability to do this?
Pig-nose holes! 
I like that!
I never bent my finger to cover these, always preferring to pull the finger straight off the recorder until the farthest “nostril” is uncovered.
By the way, I don’t believe recorders originally had the little doubled holes; that’s pretty much a modern convenience.
What they did have back yonder on the smaller recorders was two holes for the pinkie, one for right-handed players and one for left-handed. You’d fill whichever hole you didn’t use with wax.
–James
Credit where it’s due I stole the term pig nose from Zoob.
Back to Cæsar: I borrowed it in turn from someone else on the board.
Our C&F family trivia apart, these wall plugs (AC, no ground) do work.
I mean, the low C sharp works on double-holes recorder (it’s weak in volume, but otherwise awright), while I never managed to get a decent low Eb from any whistle.
Now, try this experience: play one of them DREC’s (decoder-recorders) while sticking TWO fingers in the pig’s nose, one each nostril.
Then what? 
Well, you tell us! 
Are you suppost to also half-hole whistles by sliding back instead of bending your finger? That’s how I’ve been doing it.
I’m not sure there is a “supposed to;” I would say do whatever works best for you.
I used to pull the finger off the whistle to half-hole; these days, I actually rock the finger to the side to half-hole on both whistle and flute.
No matter how you approach it, half-holing, especially done at speed, can be quite challenging. It takes time and practice to be able to do it cleanly and predicatably.
–James
Cran-- the only exercise for this is practice! Luckily, those notes are not used all that often and it seems that they come up mostly in slower movements of sonatas, etc so they are not really much of a problem.