I wanted to weight in as it has been a minute since anyone has commented on their experience.
I was invited to take the BMST and POSS with Exelon with 2 weeks to study. They gave me access to several websites with practice exams, which I have found to be excellent representations of the actual exam. I bought The Peterson's book on "Master the Mechanical Aptitude and Spatial Relations Test" from Amazon as study material before the exam, because I had never studied spatial relations.
For your comparison;
Before taking and of the practice tests I felt very confident in every subject except for the spatial relations. This is because I was in the top ten for my Power School class, and I was very confident with my math skills. My first attempt on the EEI tests showed that my intuition was very close.
Reading comp. I got 100% correct with plenty of time to spare. This section was especially easy as everything was also technical in nature, and very basic, so even if you're not great at reading, you're often answering very basic science or math questions (like "does heat go from hot to cold or cold to hot?").
Mechanical concepts was also very easy for me. I had plenty of time left over, and I only missed one question on the practice exam. If you did well in thermodynamics, fluids and mechanical equipment in the Navy, you'll do well here.
Math was surprisingly a time crunch. I taught math for a long time, and I've always done extremely well in math, but I only completed about 32 of the questions in the practice exam. However, I did get them 100% correct. I brushed up on my decimal multiplication and long division to help make up time.
Figural reasoning was crazy hard, in my opinion. I didn't complete them all, and I got 9/15 right in my first attempt. The patterns ranged from stupid easy to insanely difficult (especially for 30 seconds per problem). I was very worried about this section going into my official testing.
I had a very difficult time finding out any information about the BMST before I went into it. From what I found, I re-learned the unit circle and read up on basic reactor physics and theory.
Post test;
I received results that I passed the BMST but the POSS is still being graded. I found the BMST to be very, very easy. I would learn how to use trig tables and how to do common science-related conversions from memory.
POSS: SPATIAL REASONING...... I completed every section of the POSS except for spatial reasoning. I am 100% confident in every other section, but I'm worried about spatial reasoning. I finished 14/20 questions and I was completely rushed. My one regret is that I forgot to skip difficult problems, and instead tried to solve everything in order. I would definitely practice spatial problems from every available resource if you're serious about passing this exam. Also, SKIP DIFFICULT PROBLEMS. The last question I had was very easy, but I ran out of time as I was filling in the bubble. I think it is best to finish all of the easy ones, then systematically attack the moderate ones. I don't think anyone can finish all of these with 100% accuracy with any sort of consistency. The problems can be very complicated.
I'll post an update on my final results. Good luck to everyone.
*update* I passed. I still recommend skipping the difficult ones immediately and coming back to them. I'm confident that you'll complete more questions and get more correct this way.