What college courses would help with BMST and 12P Schoolhouse?

I signed a 4 year contract as 12N Horizontal Construction Engineer in hopes to reclass to 12P Prime Power Production Specialist during my reenlistment window. I am aware of how difficult the 12P schoolhouse is and have done some research of what type of education I might need to brush up on (Trigonometry, Pre Calc, Physics, Electrical Theory, etc.)

I am currently researching what type of degree I can study, or college courses I can take during my initial contract that will prep me for the BMST and 12P schoolhouse. I want to jumpstart my bachelors degree in a relevant field of study while also studying and learning what is needed to pass 12P AIT.

I have considered starting my B.S. in Mechanical Engineering or Electrical Engineering during my initial contract, but I do not want to waste what credits will come from completing the 12P schoolhouse as these can be used towards a degree as well. If anybody could give me some insight to what path I can take would be much appreciated.