For my two trampolines help, the jumping motion helps them reconnect. Usually adding water (giving them something to drink, putting them in a bath, taking them to the beach, letting them play in the kitchen sink) all helps. They absolutely love water and it provides enough sensory input to help them come out of their triggered state.
Sometimes they need physical touch, sometimes not, sometimes colouring in or doing something like baking (making bread so again sensory input). I also do things like put shaving foam on the patio doors to draw shapes and words on - the big arm movements help reconnect, and it’s sensory and a bit naughty and a bit fun so lots of laughter. We also put on loud music and dance.
There’s also research that points to things like swinging motions, hanging, climbing all help children reconnect with their physical feelings so lots of time at the park can be good in longer term emotional regulation.
Emotional literacy is important too - we play games in the car “show me your angry/happy/frustrated face” to help my kids find words for emotions, or if I sense they’re struggling we’ll talk about how they physically feel and link to feelings. Part of that is you as a parent being able to talk openly about your own feelings (when I feel worried about something my tummy hurts or my head feels busy) so they build a language for feelings. I also have some story cubes, feelings stones etc that we use to talk through the situation and the feelings they have.
Also don’t underestimate the role that routine, structure and predictability play - it’s much much easier to self regulate if you know what’s coming next, consistency isn’t your friend.