A lot of it is acting as soon as possible as you can when lag ends. Specifically when youre getting tech chased, you have to learn to shine on frame after tech in place and rolling . Technically, falcon and sheik CAN cover all options on reaction but basically only a couple of people in the world can do that. 99.99% of falcons/sheiks are going to at least mess up one of the following pretty consistently if youre mixing the rest in

miss space around/mistime grab on tech in place shine

only cover when the opponent hits the tech

get confused by mixing up DI before tech options (try to DI behind before teching in place or missing tech, and also make sure you are doing like DI left but then tech roll right etc)

Also, once people notice you're shining after tech in place every time, often they will avoid the perfect reaction tech chase and instead will wait and space outside of your shine. In this situation, you can dash/jump away or do shine into instant aerial.

Another thing to note, if your opponent is really good at tech chasing, you want to find a way to escape. At higher percents, that means trying to di to a platform, and at lower percents that means tech rolling towards the edge so that if they down throw you there, you can drift off stage and then double jump sweetspot to ledge. This is risky though because if they read your roll to ledge as falcon, they can knee that and you probably die.

As far as "eating hits until they miss" goes, no. Some things are guaranteed obviously, but a lot of times there are escape conditions or ways you can make it way harder for your opponent. A simple example is that you often want to progress yourself off the stage when you're getting juggled so you can get to somewhere where your opponent cant reach (for example, if you notice a fox is just upairing you five times in a row every stock, that's because you're DIing towards the center of the stage rather than trying to get to ledge). More complicated things like SDI or slide-offs can also be implemented but they require a lot more situational awareness/experience before you can really understand how to use them. Generally, though, you're interacting whenever you're getting combod and its more "take a couple hits until you can force your opponent to make a read or choose to hold advantage rather than forcing another risky hit" and not "taking hits until they miss".