Do what they all recommend above. With Deck Safety I reviewed through all 403 Maritime law questions for the 3M/2M exam the night before and it helped out a lot. Nav gen I went through the Nautical Astronomy before. As you are studying you will see your weak areas. I spent 40 hours one week working out every stability question in the Murphy books and never worked another one out until I was in the room at the REC. Your T- Nav and C- Nav once you have one type of problem down it doesn’t make sense to waste your time taking full tests. Get your Azimuths, Amplitudes, LAN, Lat by Polaris, Morning sun line/LAN, and your 3 Star fix down, and put them to the side. With the T- Nav I would just choose one or two different types of 2 bearing/distance off/ ETA problems a week and called it good. With the 70% tests just sit down and take one, review your worst subjects and repeat. I would sit at my part time car wash job and take a ROR in 15 mins, and a deck gen in 20 mins. I would take 2-3 of each every shift I worked. Deck Safety and Nav Gen it is nice to have reference material in front of you so you can learn how to look up and find things.