I find avoiding using the word "no" helps. I do that thing from "how to talk so kids will listen" book and say oh yes going to to park would be great. Shall we plan to go on x day. Or I wish I could go to the park, let's magic an aeroplane to get there or a magic carpet. The sillier the better appeals to my son but might not work with yours.
If ds wants a new toy or is upset because yet again he has lost a small figurine ( has to take a small toy everywhere). I make a big show of writing it down for him on his birthday or Christmas list.
If he goes aggressively for his sibling or me I keep my words to a minimum. I find it better to say the behaviour I do want rather than what I don't. So better to say "leave your brother alone" rather than stop hitting" if that doesn't work I separate them and get ds to sit with me on the stairs.
I really try (often fail) to use a firm and cross tone of voice rather than an angry shouty voice when he is hitting or pushing. This because shouting excites ds and makes things worse. And I try not to grapple with him as genus very sensory seeking and likes this too.
If there is a little window in the bad meltdown I I
Instantly reward the better behaviour with something likes to distract him so for us tickling and deep pressure squashing, a snack, the ipad can work.
Routine and preparing ds for changes help.
And doing lots of sensory stuff. So ds line squeezing play doh and scribbling with crayons and being wrapped up in a duvet. These are positive ways of him getting sensory feedback.
And we try to play outside as much as possible.
Anyway this works for us some of the time but we don't always keep it up because I'm lazy and can't be bothers sometimes. And sometimes I do everything "right" and it is not enough.