A friend of mine want to start playing flamenco guitar. So for the first time someone is asking me questions about flamenco. The pupil turns teacher. Maybe not a very good one but nonetheless...
Anyway, he asked me for some exercises to get him started.
So I thought: if I knew then what I know now...what exercises would have the biggest impact.
It’s not easy to answer.
Interestingly some of the more famous stuff you’d use less in day to day playing eg. Rasguedo. But you should try them anyway. Here are a two though that will impact you’re playing every day.

1.
It’s vital to get your fingers moving and improve you rhythmic flexibility.
So here a good exercise that does both.
Play the Phrygian scale – that’s from E across up through the ‘white’ notes (as in on a piano) so no sharps or flats.
Do that for at least 5 minutes each time you pick up the guitar. Ideally every time you pause in daily life.
Once you start being able to do it fluently get out a metronome & set it slow – maybe 50 BPM, maybe more, maybe less – it doesn’t matter.
Play the scale to a count of 2 notes per beat.
After 2 up & downs across the fretboard change to a count of 3.
Do this for 3 up & downs – which is when you return to the E on a count of 1 – and change to a count of 4.
Do this for 4 so you return to E on the count of 1. Then go to a count of 5.
This will blow your mind/make your fingers go wobbly at the knees. The odd numbers are very hard to begin with, especially 5. Our brains are so trained in 2 and 4. But eventually it will become second nature. Try to remember where the finger will stop on each 1 for the triplet (count of 3)and quintuplet (count of 5).
Slow the metronome down if you need to. Take it away if you need to (as long as you bring it back later).
But soon you’ll get fluent, your fingers will start moving more quickly and finding the right place whatever you’re playing but best of all you’ll start internalising unusual counts – which is fundamental to flamenco.
Tip: the count of 5 can be done as hip-po-pot-a-mus. And do it as much as you breath.

2.
Do arpeggios with any chord sequence you like. Change the chords, it will keep you fresh.
Do 4 notes, then with the same tempo do 6. That means P-I-M-A (thumb, 1st finger, middle, 3rd) or PIMAMI.
I suspect the arpeggio is the unsung hero of flamenco guitar.
Make sure you’re finder are curling up into your palm rather than pulling at the string. They should strike it. Try to keep your hand upright and move the angle around a bit to find different sounds and tones.
Here’s an nice progression: Dm – Bb – C – Am7 – Bmaj7 – Am – Gm7 – A.
Now go play.