help with gmat study plan!

Hello everyone, this is the first time I am posting here on the beatthegmat forum. I recently took the gmat and score a dismal 380. I had practiced for numerous month's and focused on the OG, working through all the problem's and trying to sufficiently time myself per problem as well. I also took around 7 or 8 full length practice test's and was usually okay with time. However, on test day I was just overwhelmed. I ran out of time on both section's, the quant. and the verbal and found myself spending more time than I would have liked per problem. I have a grasp on most of the concept's, but am in need of finding shortcut's to solve problem's as I found myself working through quant. problem's through long and tedious method's consuming lot's of time. I am aiming for a low 600 and am planning on taking the gmat again in a month. I was wondering if anyone had a study plan they followed to score decently in a limited amount of time, or any books that focused on shortcuts in solving problem's. I understand the concept's, but a combination of tiredness, a ac-laden room, and just thinking about the gmat day and night ruined me on test day. I was scoring around 550 on practice tests and the gmatprep test. Timing was my worst enemy, spending too much time on certain questions, and also solving question's in long and tedious way's vs. utilizing any shortcuts, and also the critical reasoning totally ate me up. Please help, it is much appreciated, and thank you for all the information offered on these forums!