8th A.F. WWII: were pilots who finished their 25 ever assinged to a new base to ferry and gargo duty?

After completing their 25, air crew were rotated to the US for re-assignment. This could mean instructing at flight or gunnery school, training new enlistees, or acting as administrative personnel. In some cases, it meant being re-assigned to another combat-bound squadron, but I think they may have needed to volunteer in order to be assigned to combat again.

I'm sure they were. Finishing the 25 combat missions did not mean you were discharged, though I think it did contribute to the points that determined when you got to be discharged.. it meant you had the option to stay or move out of the combat area. Pilots with combat experience were usually asked to teach new pilots.

Ferry duty was taken car of largely by WACs, women who served in the Army Air Corps.

12th and 15th were in the Africa campaign, correct?

I don't know the answer, but there is an 8th A.F. Museum in Savannah, GA (called the Mighty Eighth Air Force Museum); I'm sure they will have the answer

they were rotated home to help sell the war to the people and promote war bonds. watch the movie "Memphis Belle" it will explain all.