Those books are fine. I just passed TFS on the April exam with the new specs. What worked for me was doing all of the MERM companion problems related to the NCEES exam syllabus. Look at the exam specs and hit all problems that are on that list (including the ones mentioned that aren't core-TFS like pressure vessel, bolts, etc). I found the syllabus extremely accurate so be anal about hitting all the topics and focus on the percentages indicated.
After doing most of the relevant companion problems which are way harder and more complex you should have a good understanding of the material. Then focus on doing exam type problems. You should order the official NCEES practice exam (side plug I am selling it at discount see my classified).
The 6MS book is ok. It has some good problems ... I skipped the ones that weren't on the exam syllabus. Note that many of the 6MS problems are wacky or too complicated to be test-like so its not a useful book for doing a timed test or boosting test morale.
During exam I used the MERM, Lindberg Unit Conversion (great book -I used a lot), and the NCEES practice exam which had a few similar problems. I also used Cameron Hydraulic a little but I think the info I used was also in the MERM so it is not necessary.