Across the board with most Kirby footage I see a serious lack of the platform tech chase on reaction. It's an absolutely necessary addition to Kirby's punish game in the spacie match-ups. Triple R is the only one I've seen get serious mileage out of it and even then his consistency isn't where it needs to be. I'll give some platform tech chase tips from my experience.
After inputting dthrow, your first task is to react to their DI in the small amount of time before they are forced to tech. Specifically, if they DI behind, you have a four frame reaction window to input your turnaround so you're in position to grab DI behind tech in place shine, so it is important to be able to quickly recognize when they are DIing to land behind you.
Second, you have to determine whether or not they tech or missed tech. For every character, any tech input will produce a small yellow flash. Any missed tech will produce a green shockwave underneath the opponent. In my opinion this is the most important thing to watch for when you're attempting to make this determination. Observe these two gifs showing Falco's tech in place and missed tech neutral stand in slow motion.
http://i.imgur.com/brv3bPP.webm
http://i.imgur.com/Y912pjw.webm
Third, once you are aware that they have successfully teched, you must distinguish between tech in place, tech away, and tech in, as these will all have the smallest reaction windows for a successful regrab.
This imgur album shows the first five frames of Fox's tech animations in slow motion. Like I said in the video, Fox or Falco's feet are the most visually distinctive part of each animation, and watching them closely will allow you to determine their tech option as quickly as possible. If his feet stay mostly straight up in the air, it's a tech in. If his feet come apart, it's a tech in place. If his feet scrunch in towards his body, it's tech away. Internalize these animations and memorize them. LET THEM BECOME A PART OF YOU.
If you have determined that they missed tech, you have a number of options. Although it is sub-optimal, as I explained in the video, jab resetting as soon as you see missed tech will allow you to skip having react to their get up option after missed tech. However, at higher levels of play, your opponents will start SDIing the jab reset up and rolling or jumping out, which essentially ends your tech chase. A true tech chase champion never jab resets; Kirby can still react to every missed tech option on reaction on platforms without giving your opponent the opportunity to escape with SDI.
Simply waiting on missed tech is really stressful, as it forces you to rely on a lot of mental fortitude, patience, and focus. When you're just starting to practice this method you will probably lose to get-up attack or neutral stand spotdodge a lot, but don't let that discourage you. You can react to the start of Fox's get up attack animation with shield, or alternatively, you can shield as soon as you see missed tech. Once you're in shield, you will either shield the get-up attack and get a free grab, wait for them to neutral get-up and then shield grab them at the end, or react to a get up roll with a wavedash out of shield grab, wavedash out of shield smash turn grab, or simply shield grab if you're positioned correctly. If you're at a low enough percent, you can crouch as soon as you see missed tech. This allows you to crouch cancel get up attack and grab, and grabbing from a crouch is really easy so if they neutral get up you'll be fine too. If they get up roll behind you, you will have to dash backwards out of a crouch, which is a tough input to get used to but it still works.
Aside from waiting for you to screw up, spacies will often attempt to escape the tech chase by tech rolling to the edge of a platform and then DIing off the platform after your next dthrow. You can counter this by making a conscious effort to space yourself a fair distance away from the edge of the platform and relying on Kirby's BALLER standing grab range to pull them back in. I demonstrate this optimal spacing in the Kirby video I posted. If however, you end up getting a dthrow too close to the edge, and you are worried that they might be able to DI off the platform in that position, you can dash back towards the center of the platform, pivot and regrab, all within your reaction window. I demonstrate this reaction at roughly
1:04 in the video. Get used to doing this, as it will prolong your tech chase and lead to meatier damage.
I stand by the claim that you can always pummel at least once regardless of their mash speed, but if they're really good at it, you may need to buffer dthrow on the cstick while you're inputting the pummel. If they don't mash at all, feel free to pummel twice. You earned it. Treat yo'self!
If you have 20xx, which you should, the best way to practice these tech chases is to go to the modded Fourside stage, grab a random tech cpu Falco on the crane platform and then tech chase the **** out of him. The platform is large enough that you will have to have tight reactions and solid dash and JC grab inputs, but still small enough that you can cover everything. The camera angle is nice and close so you can watch for the animations, which will help you get used to seeing them. If you can get eight consecutive regrabs after the initial grab, you're a champ. If you can do that five times in a row, which is my personal record, then you're totally set.
I am still not knowledgeable enough about Kirby's punish game to say much about the best way to end tech chases, but hopefully you guys can put your heads together and figure that out. I hope this was helpful in some way.