Penmanship requires good eyesight (check), good fine motor skills (check) good manipulative skills (check). In addition to the link above look at how the pen is held and buy a plastic pencil grip with indents for 2nd finger and thumb to be placed on. (Available at education stores). Grip pen with thumb and second finger and back of pen over 1st finger knuckle. Relax 1st finger on pen (no pressure!). Try writing with 1st finger raised and not touching pen. This is an indication that pen grip is correct.
Mmm ...this really needs demonstration rather than an explanation in words! Hope this helps.