heres my experience with DDD.
so our fastest move is grab, which is frame 7. DDDs got the third best reach in the game for grabs which means youre going to be using it a lot for quick encounters on the ground. likewise, for his fastest move, thats pretty slow in comparison to literally every other character. hes also got dtilt and utilt that are also frame 7, but last longer and have different functions. with the presentation of this frame data, and an analysis of the frame data on the rest of his moves, DDD is literally the slowest character in the game in terms of startup times, although not necessarily the most laggy; however, he does indeed have overall amazing disjoint and range. this brings me to the first point of pressure evation: prevention. you really have to have a mind for the space that your opponent can cover, and how quickly they can cover it. by utilizing ftilt, jabs, grabs, and waddle dees, you can cover space through a range and prevent the opponent from getting in. (DDDs jab is a seriously underated move, despite how slow it is. the coverage, reward, and low commitment are amazing).
now when your opponent DOES get in, DDD still has a few tools OOS and up close to take some of the heat off and avoid things like CCs and shield pressure. dair is relatively good for breaking through CCs and landing a set up for yourself. its not the quickest, but if you full hop with it, you can quickly DJ out of it far before landing, keeping you pretty safe. when speed IS needed, the obvious choice is grab. there is indeed another option OOS however which ive seen like, nobody exploit yet: his up B. on stages with platforms, you can (relatively easily actually) up b, then press down to cancel it, and slip of the edges of the platforms to cancel the lag and be able to follow up immediately. armor comes out on frame 7, and DDD can give some good slide distance if you hold a direction before leaving the ground. this can be a good retreat option if you have characters really good at mixing up shield pressure that can make landing grabs hard, or if they are at your backside. its not always a go to option, but it IS an option at times, and can get you out of sticky situations more often then you may think, considering the different possibilities of canceling in different directions off platorms (or even without, if you are confident you will hit them, and end lag wont hurt you), as well as letting the duration of the move pan out and let the landing stars give you potential coverage for safety. you will definitely get punished for using it too much, but like i said, it helps turn a gaping weakness into a more manageable one.