Here are some examples (including photos) of warm up activities to support fine motor skills and tool control with children. I would suggest completing these at the beginning of each handwriting and art session in order to develop children’s muscles and support the steadiness of their grip. You may also want to see my assessment of art guidance, which is completely free: https://www.tes.com/teaching-resource/art-assessment-guidance-what-makes-good-art-13012093 or my whole school CPD on diversifying artists: https://www.tes.com/teaching-resource/art-cpd-for-primary-school-teachers-diversify-the-artists-you-study-13012106. Don’t forget to make a review!