What if any splints may help trigger finger (middle finger of right hand? When should they be worn?

Splint and elevate. Splits that hold the hand in the position of function (holding a soda pop can) achieve rest that may minimize the tendon swelling. Elevation of the hand particularly at night combine with short term anti-inflammatories may help.
Distal joint splint. Don't over treat i.E splinting the distal joint (so-called dip) is enough along possibly with anti inflammatories and localized massage. If you over treat you can end up with unnecessary finger stiffness.