Making sure that fingers and tongue are coordinated is the first step in achieving clean articulation. It will help to practice passages slurred first to carefully listen for clean and even finger changes. If the fingers are not even, there is no way articulated passages can be even. Practice with varied articulation: slur 2/tongue 2, reverse that as well, and then try all articulated...SLOWLY. Speeding up can be worked on in small bursts, (using chunking to break up the passage) ...then put each piece back together. Sometimes the problems of coordination are NOT the tongues fault: it's rushing fingers causing the problem. The tongue should not move a great deal inside the mouth and should not cut notes off...Keep listening. Because there is no way to SEE articulation, we must rely on our ears to fix the problems.
Piccolo Finger Technique
Because of the piccolo's smaller size, finger technique needs to be slightly modified. Some tricky third octave passages on the flute can get a great boost by using harmonics, but because of the greater resistance on piccolo, often this option is not quite as available to us, although I am able to use this as an option many times. I try to play a little more on the finger tips, curving the fingers slightly more on piccolo since the keys are smaller and there are no open holes to worry about covering. Think about incorporating trill fingerings for extremely fast passages. Keep fingers even closer to the keys than the flute. Always, start slow and small: slower tempo and small segments of the passage (a beat is enough at the beginning). Link together as you teach the passage to your fingers, and gently ramp up the tempo. I enjoy playing the passage from right to left for a 'new' way of looking at it(this also heightens the concentration). Keep earplugs handy as you do this: Extended piccolo practice is tough on the ears.