I am aiming for national level skill. I want to be able to use my front kicks more fluently and naturally. Are there any good drills for that?
Basing this answer on a TaeKwonDo front kick
With most things in life the best way to improve is to practice it.
Breaking If you are looking to break with a front kick then technique is crucial.
Ensure that your knee is coming up high (and then dropping slightly as the foot fires forward to make the foot travel straight).
Make sure you are making contact with the ball of the foot
Hips must stay parallel - if you twist the kicking hip forwards the power will slip off to the side.
practice - kicking the air is good for balance and ensuring technique is correct. Mix fast and slow motion kicking to build the muscle memory. Once your technique is good then kick the pads. Kicking off the back leg will be more generally be more powerful because your weight is travelling forward.
Sparring Usually this requires more speed/flexibility and the technique can be sacrificed a little.
Still do everything above - The front kick still stays the same - if you want to be a world class sparrer then you need to be a world class kicker.
A couple of pointers for using this in sparring - the front leg is quicker and for much closer range so can be used to get in or out of hand/punch range. By pushing your hip forward you can get a little more height/distance which may make the difference between a chest shot and a head shot.
practice - use sparring sessions to practice the techniques you want to improve - set yourself a target for the lesson (or each spar) such as "I will score a front kick" or "I will use front kicks to open up punching opportunities". If you don't use sparring training sessions to try new things - you will forever and ever spar the same way
Practice your kicks as if you are moving in slow-motion. While doing so, focus on perfecting your form. Proper posture, balance, and skeletal alignment are key to optimizing your technique. Speed and power will follow.
I cannot stress this enough, but practice your kicks and footwork at the same time. If you are looking to be a high level competitor in tournament or other contact competition you need to be able to fluidly attack mid-stride. This is one of the best ways to increase one's 'speed' in combat. Practice moving and kicking until you no longer have to think about the details.
Along with practicing your footwork, work on kicking at a moving target. Work with a partner who is holding a kicking target and have them move like an opponent (alternating defensive and offensive footwork). When training alone you can use a ball suspended from a string from the ceiling of your training area (tennis balls are a great for this). The ball is a small(ish) target for you work on fine motor control, and it can swing like a pendulum or in circles. You can also practice your footwork circling around and reacting to the balls movements.
Getting good at kicks is about drilling them a lot and here are a few recommendations as to how to go about doing it.
To boost fluidity in front kicks a person will need to be flexible as lacking flexibility will create resistance and slow them down. At a minimum ensure you can touch the toes without the knees bending but the ultimate level is to be able to fold so the palms touch the floor & the face touches the knees.
Fluidity & speed
Kicking is an art form and the best kickers can launch kicks from unexepcted angles that change direction in mid flight yet are still powered. Practising this is with core and varied kicking drills. For example a front thrust kick can be practiced by playing with different heights & stagering the timing. Then additional variations can be included eg it might start like a thrust kick but turns into an axe kick. But underpinning all this is doing a lot of kicks (aim for 1000+) in a practice session. Not necesarily full force and without breaks but done in almost a playful experimental level. Also play with speed. This could include landing a set number of kicks in a time block and then attempting to beat your time.
This is a tricky one to do solo. There are methods but I recommend finding good sparring partners & getting them to drill your footwork, avoidance and counterkicking. The greatest timing in a kick is when an opponent is delivery a kick they believe will land as they thrust for power only to hit the air. They are for a split second vulnerable and if a counter kick lands, it will hurt & score a lot of points.
Power & Balance
Often overlooked and this might not be as important in certain competitions but power training does help with speed, timing and balance. This includes squats and lunges but I find that leg pistols are very effective. This can then be augmented with heavy bag kicking to ensure the foundation is still there as kicks loose power when off balanced.
A further way to power kicks is to create perfect balance play. One excercise is to lift the leg, extend it and piston it back and forth an inch. Do this for as long as possible. When comfortable then do it on a brick wall just raising the leg and lightly tapping.