More heavy work, and fewer corrections. Heavy work simply means activities that push or pull against resistance, and it is the most reliably calming thing you can offer a dysregulated nervous system. Carrying the grocery bags, pushing a laundry basket across the floor, animal walks down the hallway, hanging from a bar at the park, a long squeeze before a hard transition.
For hand skills, resist the urge to go straight to worksheets. Strength and control build through play long before they show up in handwriting: tearing paper, squeezing spray bottles, picking up small objects with tongs, working with putty or thick dough, drawing on a vertical surface like paper taped to a wall or a bath crayon on the tub wall, which builds the shoulder stability that neat writing depends on.
For clothing battles, give the sensory system information ahead of time rather than negotiating in the moment. Firm pressure before dressing, letting your child choose between two acceptable options, and turning shirts inside out to move seams away from skin all cost you nothing and often help immediately.
One more thing that helps and costs nothing at all: notice out loud when a hard moment goes well. Children who struggle with these skills hear a great deal about what they got wrong.