Start with high-confidence handwriting books, then narrow by subgenre or adjacent topics.
My Big Activity Workbook
Roger Priddy
Numbers 1-50 (wipe Clean Workbook)
Big Handwriting Practice Workbook for Kids
Crystal Radke
Montessori: Letter Work
Bobby George, June George
My First Learn-to-write Workbook
The Print Penmanship Workbook for Kids
My First Book of Patterns Pencil Control: Patterns Practice Book for Kids (pattern Writing)
Wonder House Books