noob question: dealing with d+p

You don't really 'beat' 2P. You should block it and use the advantage. Doing anything else is a risk that someone who knows what they're doing will want you to take.

If you're already in an advantaged situation (you've block an attack, had your standing jab blocked, etc) Your 2P will land before your opponents assuming you both acted immediately. If you have enough advantage you can even use a fast mid for greater reward. The key is recognising when you're at advantage or disadvantage. You can turn detailed stats on in replays to see.

 

Low punch is high-risk/(somewhat)low reward in FS. While you can't always 'beat' low punch (you can't punish it, relying solely on counter is always a unfavorable risk, and evading it doesn't always lead to a guaranteed punish either), the idea that you should push across is to 'convince' your opponent that using low punch isn't such a good idea.

1. Using on-block frames for your benefit:
This is above the heads of most players that are new to FS, and even I have only started to really catch on to this. But 2P is universally -5 on block -- this means if you block a 2P, you can put your opponent into a mixup (immediately) afterward.

In my mind, in this situation, i personally like to think that my opponent is in Nitaku('two-choice') situation. In short terms, a Nitaku is a situation where you FORCE your opponent to choose between eating a mid or a throw. This technically isn't true, because at -5 (and even moreso from crouch), your opponent can perform a 'from-crouch fuzzy guard' to beat both options. But in reality, unless you are playing an obviously good opponent (read:you're not), they aren't going to use this in a match (if they even know how to do it )

Long-story short, after blocking a 2P, a good option to hit them with is elbow (6P for Aoi, dunno Shun's). It's the safest and fastest mid, and will beat alot of options that they try to do afterward (such as if they try to attack,crouch block,throw). If they get hit, then congratulations, you have +6 or +7, which means you can force ANOTHER mixup on them for free. If they block, you're safe. If they evade, it will be very difficult for them to punish you (read:they won't). By the next time you block another 2P of theirs, you have a better idea of how they will react, and you can punish them.

2. Low crushes:
Low crushes are attacks that are immune to opponent's low attacks, causing them to whiff, which often leads into a counter hit. Most characters have one or more low crushes. You already mentioned one of Shun's, 6+K+G. (True) Low Crushes are scary, because they are often safe, and even moreso because they can be used even in heavy frame disadvantage. Shun's 6+K+G can be used even way down in -8 disadvantage! They also usually lead into a combo for big damage, so there's a big reward for calling out your opponent's 2P with Low crushes! So in other words, if you feel your opponent likes to 2P after they block one of your moves, use a low crush to blow it up for way more damage than they would have gotten for hitting you with a 2P

Aoi is special -- fighting against low attacks is a weakness of hers in general, and she doesn't have a true low crush (besides, what, jump kick? ). But that's fine, because she can still block 2Ps and use the frame advantage. She also has Low reversals, another option that most characters don't have. Which leads me into.....

3. Low reversals:
If you get into a situation where you ABSOLUTELY 200 PERCENT KNOW YOUR OPPONENT IS GOING TO 2P YOU, then this is when using low reversals are a good option. Low reversals don't often have as big of rewards as the first two options (the damage is lower than low crush-->combo, and you normally don't get the frame advantage to go for a mixup, like blocking a 2P). But the damage you get on a correct read is immediate and guaranteed (~30 DMG for Aoi low reversal + guaranteed followup ground throw attempt/3P ground attack(I think)). Some other characters, such as Sarah have Low Parries that are high risk/high reward, but offer heavy frame advantage for guaranteed launch. Some other characters, such as Wolf, have low punch parries that can change ring position, which is great for forcing backturned stance or a ringout.


You actually have PLENTY of options for blowing up Low punch, you just have to explore and remember them. And I GUARANTEE you those options do more than the measily 8 DMG that a successful 2P that hits you get

 

I can't emphasize enough, your default response should be blocking the 2P then using the advantage to apply your own offence. All of the above is trying to run before you can crawl. Remember that low punch is a universal option and the best answer is the same for every character.

 

If the 2P hits you then its your 'turn' to defend. If it hits you CH (yellow flash) then you're firmly in the mid/throw guessing game and attacking at this point is risky, but exactly what you should do if you think they opponent willl throw. There is nothing wrong or scary about being hit with 2P. It doesn't do that much damage and puts you on the defensive. I'd be far more worried about letting such a good common move force you into taking dangerous risks.

Lets say we use your example of PPP. Usually if you PPP you're at DISADVANTAGE on HIT. In this instance you have no way to interrupt the 2P. Attacking at this point is viable, but you should understand that it's a massive risk. This is where recognising when you're advantage or disadvantage comes in.

Trying to use the sabaki or 66K or even the counter is also risky. The attacks are slow and specific in what they beat. The counters? Sure if you absolutely know what the opponent is going to do. If you're not sure then the risk is unnecessary.

 

It's +4 on hit. -5 on block. The difference is small, but important.