I just took MPJE this morning. I don't feel like the test was as difficult as NAPLEX, but I feel it was so much more confusing. So many times I felt like multiple answers could be right, save for a small detail I 'might' be missing after reading so much state/fed/CSA law. Hopefully I'll get the score soon, already passed NAPLEX and ready for this crap to be over.
I really have no idea how I would prepare differently if I was forced to take it again, I read through every law, did practice questions, attended the school provided class, and I still feel like I was tripped up by the minutiae and wording.
As for OP's question, I studied straight on for 3 days, 10 hours a day before my test, including study group. Prior to it was a couple hours here and there, but I was more concerned about the NAPLEX so that got the brunt of my attention. We will see next week if it was enough.